Cut back on tough fish (8)
I believe the answer is:
pilchard
'fish' is the definition.
(pilchard is a kind of fish)
'cut back on tough' is the wordplay.
'cut' becomes 'clip' (clip is a kind of cut).
'back' is a reversal indicator.
'on tough' becomes 'hard' ('hard' is associated in meaning with 'tough'. I am not sure about the 'on' bit.**).
'clip' in reverse letter order is 'pilc'.
'pilc'+'hard'='PILCHARD'
Can you help me to learn more?
(Other definitions for pilchard that I've seen before include "Fish of herring family" , "type of fish" , "Small sea fish related to the herring" , "Item of seafood" , "Small fatty fish, usually tinned" .)