Something to shut up and eat? (4)

I believe the answer is:

clam

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'eat?' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how they can define each other.

I can't explain the remainder of the clue.

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(Other definitions for clam that I've seen before include "Aquatic creature" , "Mollusc with tightly-closed shell" , "Edible shellfish" , "Large marine bivalve" , "Proverbially reticent marine mollusc" .)

I've seen this clue in the Evening Standard.

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