Fish appearing in dock reversed shortage (7)

I believe the answer is:

pollack

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

'dock reversed shortage' is the wordplay.
'dock' becomes 'lop'.
'reversed' says the letters should be written backwards.
'shortage' becomes 'lack' (I've seen this before).
'lop' reversed gives 'pol'.
'pol'+'lack'='POLLACK'

'appearing in' acts as a link.

(Another definition for pollack that I've seen is " Food fish of the cod family".)

I've seen this clue in The Times.

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