Gather you must release the fish (3)

I believe the answer is:

gar

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

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

(Other definitions for gar that I've seen before include "something fishy here" , "Creature" , "swimmer" , "Type of fish" , "Pike-like fish" .)

I've seen this clue in the Evening Standard.

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