CERE is a 4 letter word that starts with C.

1. \Cere\, n. [L. cera wax: cf. F. cire.] (Zo["o]l.)
   The soft naked sheath at the base of the beak of birds of
   prey, parrots, and some other birds. See {Beak}.
   
   

2. \Cere\, v. t. [imp. & p. p. {Cered}; p. pr. & vb. n.
   {Cering}.] [L. cerare, fr. cera wax: cf. F. cirer.]
   To wax; to cover or close with wax. --Wiseman.