Hunter parted, or set off (8)
I believe the answer is:
predator
'hunter' is the definition.
(I've seen this before)
'parted or set off' is the wordplay.
'set off' indicates an anagram.
'parted'+'or'='partedor'
'partedor' with letters rearranged gives 'PREDATOR'.
(Other definitions for predator that I've seen before include "Carnivorous animal - teardrop (anag)" , "Hunter" , "Marauder" , "Animal that preys on others" , "eagle, for one" .)