Deduce from the fish caught (6)

I believe the answer is:

gather

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'deduce' is the definition.
(I've seen this in another clue)

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

(Other definitions for gather that I've seen before include "Get together" , "The rag (anag.)" , "Accumulate, amass" , "Assemble or glean" , "Come together for the rag" .)

I've seen this clue in the Evening Standard.

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