Rooster (4)
I believe the answer is:
cock
'rooster' is the definition.
(I know that rooster can be written as cock)
This is all the clue.
(Other definitions for cock that I've seen before include "Pull back a gun's hammer in readiness to shoot" , "Tilt (one's head to one's side)" , "sunshine" , "Hen's mate" , "Adult male bird" .)