Shuts up and gets on (6)

I believe the answer is:

boards

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'gets on' is the definition.
('board' can be a synonym of 'get on')

I cannot understand how the rest of the clue works.

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(Other definitions for boards that I've seen before include "Tread them in the theatre" , "Goes on" , "sections of timber" , "Gets on (a ship)" , "Adsorb (anag)" .)

I've seen this clue in the Evening Standard.

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