Fish for immediate payment (3)

I believe the answer is:

cod

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

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

(Other definitions for cod that I've seen before include "No payment in advance" , "Common food fish" , "Kid" , "Cash on delivery, in short, for this fish" , "method of payment" .)

I've seen this clue in the Evening Standard.

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