Fattening fish? (7)

I believe the answer is:

bloater

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

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

(Other definitions for bloater that I've seen before include "that will more than fill one up" , "Fish" , "Partially dried herring" , "Buckling" , "Something fishy" .)

I've seen this clue in the Evening Standard.

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