Bully an animal (3)
I believe the answer is:
cow
This clue is a double definition.
'bully' is the first definition.
(cow can mean to bully or oppress)
'an animal' is the second definition.
(I know that cow is a type of animal)
(Other definitions for cow that I've seen before include "Subdue with threats or force" , "Overawe" , "Female domestic mammal" , "Subdue in bovine manner?" , "Female farm animal" .)