Crossword Genius

Mastered - the art of remaining silent? (8,2)

Ross

I believe the answer is:

buttoned up

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'silent?' is the definition.
(I've seen this before)

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(Other definitions for buttoned up that I've seen before include "Silent" , "taciturn manner" , "presumably lacking zip!" , "made more emphatic" , "concluded satisfactorily" .)

I've seen this clue in the Evening Standard.
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