Dock sent back tough fish (8)

I believe the answer is:

pilchard

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'fish' is the definition.
(pilchard is a kind of fish)

'dock sent back tough' is the wordplay.
'dock' becomes 'clip' (I can't justify this - if you can you should give a lot more credence to this answer).
'sent back' is a reversal indicator.
'tough' becomes 'hard' (similar in meaning).
'clip' reversed gives 'pilc'.
'pilc'+'hard'='PILCHARD'

Can you help me to learn more?

(Other definitions for pilchard that I've seen before include "'Small fatty fish, usually canned (8)'" , "Item of seafood" , "type of fish" , "Fish of herring family" , "Edible herring relative" .)

I've seen this clue in The Independent.

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