Marine predator creates warlike hell (6,5)
I believe the answer is:
killer whale
'marine predator' is the definition.
(I've seen this before)
'creates warlike hell' is the wordplay.
'creates' indicates an anagram.
'warlike'+'hell'='warlikehell'
'warlikehell' anagrammed gives 'KILLER WHALE'.
(Other definitions for killer whale that I've seen before include "Marine mammal" , "Predatory relative of dolphin" , "Orca" , "Marine predator" .)