Shuts up and gets down to it (7)

I believe the answer is:

buckles

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'shuts' is the definition.
The definition and answer can be both to do with contact as well as being verbs in their -s form.
Maybe there's an association between them I don't understand?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for buckles that I've seen before include "Clips for fastening belts" , "Secures" , "damages" , "Belt fasteners" .)

I've seen this clue in the Evening Standard.

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