Fowl's crest (4)
I believe the answer is:
comb
'fowl's crest' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for comb that I've seen before include "Something with teeth (for the hair!)" , "Go over" , "Untangle (hair)" , "Search methodically" , "Groom; search" .)