Those shown with a smile? (5)

I believe the answer is:

teeth

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'smile?' is the definition.
The answer and definition can be both related to bodily activities as well as being verbs in their base form.
Maybe they are linked in a way I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for teeth that I've seen before include "genuine power" , "Choppers" , "One may be armed to them" , "Feature of an effective bill" , "Effective power" .)

I've seen this clue in the Evening Standard.

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