Royal stallion? (4)
I believe the answer is:
sire
This clue might be a double definition.
'royal' is the first definition.
(sire is a kind of royal)
'stallion?' is the second definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for sire that I've seen before include "Male parent of an animal" , "Bear" , "Stallion; beget" , "Male parent of a horse, for example" , "Old form of address to king - rise to it" .)