Fighter of an animal, say (9)
I believe the answer is:
guerrilla
'fighter' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for guerrilla that I've seen before include "Member of politically-motivated fighting group" , "Such tactics" , "political insurgent" , "One fighting" , "Person who fights as one of small independent group" .)