Initial payment for fish! (3)

I believe the answer is:

cod

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'for fish' is the definition.
(type of fish)

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

(Other definitions for cod that I've seen before include "North Atlantic fish" , "No payment in advance" , "Fish noted for liver oil" , "Kid" , "One caught in the deep maybe" .)

I've seen this clue in the Evening Standard.

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