You may part with this part of fowl (4)
I believe the answer is:
comb
I believe this is a double definition.
'you may part with this' is the first definition.
(a comb can be used to give one's hair a parting)
'part of fowl' is the second definition.
(crest on the head of a fowl)
(Other definitions for comb that I've seen before include "Search methodically" , "Toothed instrument" , "Toothed object for tidying hair" , "Toothed implement - search (the area)" , "Tidy (hair); some honey" .)