Animal's male parent (4)
I believe the answer is:
sire
'animal's male parent' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sire that I've seen before include "Male parent of a horse, for example" , "Old form of address to king - rise to it" , "Male parent of an animal" , "Male parent of, say, horse" , "Bear" .)