Reeks from mackerels in chowder (4)

I believe the answer is:

clam

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'chowder' is the definition.
(clam chowder is a kind of chowder)

I can't explain the remainder of the clue.

(Other definitions for clam that I've seen before include "Mollusc, one proverbially reticent" , "ringing noise produced by > very reticent type" , "Large shellfish with hinged shell" , "Quahog" , "What could grip" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.

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