WordNet (r) 3.0 (2006):

clappers
    n 1: a percussion instrument consisting of a pair of hollow
         pieces of wood or bone (usually held between the thumb and
         fingers) that are made to click together (as by Spanish
         dancers) in rhythm with the dance [syn: bones,
         castanets, clappers, finger cymbals]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "clappers":
   battery, bells, bones, castanets, celesta, chime, chimes,
   crash cymbal, cymbals, finger cymbals, gamelan, glockenspiel, gong,
   handbells, idiophone, lyra, maraca, marimba, metallophone,
   orchestral bells, percussion, percussion instrument, percussions,
   percussive, rattle, rattlebones, sizzler, snappers, tam-tam,
   tintinnabula, tonitruone, triangle, tubular bells, vibes,
   vibraphone, xylophone