What describes making fake hake and cod? (4)

I believe the answer is:

fish

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'cod?' is the definition.
(cod is a kind of fish)

I don't understand how the rest of the clue works.

(Other definitions for fish that I've seen before include "Trawler's catch" , "To try to catch" , "occupant of tank" , "Cod, dab, eel and ray" , "Angle; trawl" .)

I've seen this clue in The Independent.

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