The Collaborative International Dictionary of English v.0.48:

Clacker \Clack"er\, n.
   1. One who clacks; that which clacks; especially, the clapper
      of a mill.
      [1913 Webster]

   2. A claqueur. See Claqueur.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "clacker":
   Klaxon, boiler factory, boiler room, bull-roarer, catcall,
   cherry bomb, clack, clapper, cracker, cricket, firecracker, horn,
   noisemaker, rattle, rattlebox, siren, snapper, steam whistle,
   ticktack, whistle, whizgig, whizzer