The Collaborative International Dictionary of English v.0.48:

Clerk \Clerk\ (kl[~e]rk; in Eng. kl[aum]rk; 277), n. [Either OF.
   clerc, fr. L. clericus a priest, or AS. clerc, cleric, clerk,
   priest, fr. L. clericus, fr. Gr. klhriko`s belonging to the
   clergy, fr. klh^ros lot, allotment, clergy; cf. Deut. xviii.
   2. Cf. Clergy.]
   1. A clergyman or ecclesiastic. [Obs.]
      [1913 Webster]

            All persons were styled clerks that served in the
            church of Christ.                     --Ayliffe.
      [1913 Webster]

   2. A man who could read; a scholar; a learned person; a man
      of letters. [Obs.] "Every one that could read . . . being
      accounted a clerk." --Blackstone.
      [1913 Webster]

            He was no great clerk, but he was perfectly well
            versed in the interests of Europe.    --Burke.
      [1913 Webster]

   3. A parish officer, being a layman who leads in reading the
      responses of the Episcopal church service, and otherwise
      assists in it. [Eng.] --Hook.
      [1913 Webster]

            And like unlettered clerk still cry "Amen". --Shak.
      [1913 Webster]

   4. One employed to keep records or accounts; a scribe; an
      accountant; as, the clerk of a court; a town clerk.
      [1913 Webster]

            The clerk of the crown . . . withdrew the bill.
                                                  --Strype.
      [1913 Webster]

   Note: In some cases, clerk is synonymous with secretary. A
         clerk is always an officer subordinate to a higher
         officer, board, corporation, or person; whereas a
         secretary may be either a subordinate or the head of an
         office or department.
         [1913 Webster]

   5. An assistant in a shop or store. [U. S.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

clerk
    n 1: an employee who performs clerical work (e.g., keeps records
         or accounts)
    2: a salesperson in a store [syn: salesclerk, shop clerk,
       clerk, shop assistant]
    v 1: work as a clerk, as in the legal business

Moby Thesaurus II by Grady Ward, 1.0:

210 Moby Thesaurus words for "clerk":
   Bible clerk, Bible reader, CA, CPA, DD, Doctor of Divinity,
   Federal, Holy Joe, abbe, academician, accountant,
   accountant general, acolyte, actuary, agent, almoner, amanuensis,
   anagnost, archivist, auditor, baggage agent, bank accountant,
   bank examiner, beadle, bedral, bookkeeper, bookman, business agent,
   calculator, calligrapher, capitular, capitulary,
   certified public accountant, chaplain, chartered accountant,
   chirographer, choir chaplain, churchman, churchwarden, claim agent,
   classicist, clergyman, cleric, clerical, colossus of knowledge,
   commercial agent, commission agent, comptroller, consignee,
   controller, copier, copyist, cost accountant, cost keeper, curate,
   cure, customer agent, deacon, deaconess, divine, documentalist,
   dupe, ecclesiastic, elder, elderman, engraver, factor, fed,
   federal agent, filing clerk, floorwalker, freight agent,
   functionary, general agent, genius, giant of learning, humanist,
   implement, ink spiller, inkslinger, instrument, insurance agent,
   journalizer, land agent, law agent, lay elder, lay reader,
   learned clerk, learned man, lector, lecturer, letterer, librarian,
   literary agent, literary man, litterateur, loan agent,
   lover of learning, man of God, man of learning, man of letters,
   marker, mastermind, military chaplain, mine of information,
   minister, news agent, notary, notary public, official, padre,
   parish clerk, parliamentary agent, parson, passenger agent, pastor,
   pen, pencil driver, penman, penner, philologist, philologue,
   philomath, philosophe, philosopher, polyhistor, polymath, preacher,
   precentor, press agent, prothonotary, pundit, puppet,
   purchasing agent, reader, real estate agent, reckoner,
   record clerk, recorder, recording secretary, recordist, rector,
   register, registrar, reverend, ruling elder, sacrist, sacristan,
   sales agent, sales engineer, sales force, sales manager,
   sales personnel, salesclerk, salesgirl, saleslady, salesman,
   salespeople, salesperson, saleswoman, savant, scalper, scholar,
   scholastic, schoolman, scorekeeper, scorer, scribbler, scribe,
   scrivener, secretary, seller, selling agent, servant of God,
   sexton, shames, shepherd, shop assistant, shop clerk, sidesman,
   sky pilot, special agent, station agent, stenographer, steward,
   stonecutter, store clerk, student, succentor, suisse,
   supply clergy, supply minister, teaching elder, the Reverend,
   the very Reverend, theatrical agent, thurifer, ticket agent,
   ticket scalper, timekeeper, tonsured cleric, tool, transcriber,
   travel agent, verger, vergeress, walking delegate,
   walking encyclopedia, word-slinger, writer



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CLERK, commerce, contract. A person in the employ of a merchant, who attends

only to a part of his business, while the merchant himself superintends the
whole. He differs from a factor in this, that the latter wholly supplies the
place of his principal in respect to the property consigned to him. Pard.
Dr. Com. n. 38, 1 Chit. Pract. 80; 2 Bouv. Inst. n. 1287.



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CLERK, officer. A person employed in an office, public or private, for
keeping records or accounts. His business is to write or register, in proper
form, the transactions of the tribunal or body to which he belongs. Some
clerks, however, have little or no writing to do in their offices, as, the
clerk of the market, whose duties are confined chiefly to superintending the
markets. In the English law, clerk also signifies a clergyman.



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CLERK, eccl. law. Every individual, who is attached to the ecclesiastical
state, and who has submitted to the ceremony of the tonsure, is a clerk.