It's usual amongst men or male animals (6)
I believe the answer is:
normal
'it's usual' is the definition.
(I've seen this in another clue)
'amongst men or male animals' is the wordplay.
'amongst' says the answer is hidden in the clue.
'NORMAL' is hidden within 'men or male animals'.
(Other definitions for normal that I've seen before include "Standard, expected" , "Standard - well-adjusted" , "Customary" , "it's what you'd expect" , "Conforming to what is usual" .)