Gags and keeps in confinement (5,2)

I believe the answer is:

shuts up

I'm a little stuck... Click here to teach me more about this clue!

This clue could be a double definition.

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

'keeps in confinement' is the second definition.
The definition and answer can be both to do with communicating as well as being verbs in their -s form.
Perhaps you can see an association between them that I don't see?

'and' is the link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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