Young male horse (4)
I believe the answer is:
colt
'young male horse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for colt that I've seen before include "with a hefty kick?" , "pistol" , "Type of revolver and a young horse" , "Young male horse or cowboy revolver" , "Youngster" .)