Ferocious fish (7)
I believe the answer is:
piranha
'ferocious fish' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for piranha that I've seen before include "fish chewed up" , "Voracious eater" , "Ferocious fish" , "This predator" , "Sharp-toothed fish" .)