Fish cut back severely (8)
I believe the answer is:
pilchard
'fish' is the definition.
(I know this)
'cut back severely' is the wordplay.
'cut' becomes 'clip' (clip is a kind of cut).
'back' is a reversal indicator.
'severely' becomes 'hard' (synonyms).
'clip' back-to-front is 'pilc'.
'pilc'+'hard'='PILCHARD'
(Other definitions for pilchard that I've seen before include "Fish of herring family" , "Small sea fish related to the herring" , "'Small fatty fish, usually canned (8)'" , "Edible herring relative" , "Small fatty fish, usually tinned" .)