Hardly a thing to keep baby quiet? (6)

I believe the answer is:

rattle

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'quiet?' is the definition.
The answer and definition can be both to do with perception as well as being verbs in their base form.
Maybe there's a link between them I don't understand?

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for rattle that I've seen before include "Gurgling sound in throat" , "Shake - baby's toy" , "Noisy baby's toy" , "Venomous creature's warning" , "Sir Simon --, conductor" .)

I've seen this clue in the Evening Standard.

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