Restraint removing front feather from cockerel (6)
I believe the answer is:
hackle
'feather from cockerel' is the definition.
(feather from the neck of a cockerel)
'restraint removing front' is the wordplay.
'restraint' becomes 'shackle' (shackle is a kind of restraint).
'removing front' means to remove the first letter.
'shackle' with its first letter taken away is 'HACKLE'.
(Other definitions for hackle that I've seen before include "Feather forming part of an angler's fly" , "Feather wound around a fishing fly" .)