Fish to fatten you? (7)

I believe the answer is:

bloater

I'm a little stuck... Click here to teach me more about this clue!

'fish' is the definition.
(I know that bloater is a type of herring)

I cannot 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" , "Buckling" , "Cured herring" , "food" , "Fish" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.