Show signs of being rattled? (5)

I believe the answer is:

shake

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'show signs' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe there's an association 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 shake that I've seen before include "Jolt or agitate" , "Flavoured milk drink" , "Shiver" , "wave" , "moment" .)

I've seen this clue in the Evening Standard.

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