Foal (4)
'foal' is the definition.
(colt is a kind of foal)
This is the entire clue.
(Other definitions for colt that I've seen before include "Handgun -- young horse" , "Young animal" , "Young player" , "Young stallion" , "member of the youth team" .)
'foal' is the definition.
(filly is a kind of foal)
This is all the clue.
(Other definitions for filly that I've seen before include "Female horse under four years old" , "Young mare" , "Young female horse" .)