Strangle fish with bad cut (8)
I believe the answer is:
garrotte
'strangle' is the definition.
(garrotting is a kind of strangling)
'fish with bad cut' is the wordplay.
'fish with' becomes 'gar' (gar is a kind of fish. I am not sure about the 'with' bit.).
'bad' becomes 'rotten' (similar in meaning).
'cut' means to remove the last letter.
'rotten' with its final letter taken off is 'rotte'.
'gar'+'rotte'='GARROTTE'
(Other definitions for garrotte that I've seen before include "Strangle with wire/cord" , "Apparatus for execution by strangulation" , "Apply throttle" , "Strangle with wire or cord" , "weapon" .)