The Collaborative International Dictionary of English v.0.48:

Clause \Clause\, n. [Obs.]
   See Letters clause or Letters close, under Letter.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Clause \Clause\, n. [F. clause, LL. clausa, equiv. to L.
   clausula clause, prop., close of ? rhetorical period, close,
   fr. claudere to shut, to end. See Close.]
   1. A separate portion of a written paper, paragraph, or
      sentence; an article, stipulation, or proviso, in a legal
      document.
      [1913 Webster]

            The usual attestation clause to a will. --Bouvier.
      [1913 Webster]

   2. (Gram.) A subordinate portion or a subdivision of a
      sentence containing a subject and its predicate.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "clause":
   adjectival phrase, article, back matter, bill, book,
   boundary condition, calendar, catch, chapter, column,
   companion bills amendment, condition, construction, donnee,
   dragnet clause, enacting clause, escalator clause, escape clause,
   escape hatch, expression, fascicle, fine print, folio,
   front matter, gathering, given, grounds, headed group,
   hold-up bill, idiom, idiotism, installment, joker, kicker,
   limiting condition, livraison, locution, manner of speaking,
   motion, noun phrase, number, obligation, omnibus bill, page,
   paragraph, parameter, part, passage, peculiar expression, period,
   phrasal idiom, phrase, prerequisite, privileged question,
   provision, provisions, proviso, question, requisite, rider,
   saving clause, section, sentence, serial, set phrase, sheet,
   signature, sine qua non, small print, specification,
   standard phrase, stipulation, string, syntactic structure, term,
   terms, text, turn of expression, turn of phrase, ultimatum, usage,
   utterance, verb complex, verb phrase, verbalism, verse, volume,
   way of speaking, whereas, word-group