Drop in at the local library? (4)

I believe the answer is:

call

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'drop' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?

'in at the local library?' is the wordplay.
'in' says the answer is hidden in the clue.
'CALL' is hidden in the letters of 'at local library'.

Can you help me to learn more?

(Other definitions for call that I've seen before include "Phone; cry" , "That is enough" , "Ring or visit" , "Summon; shout" , "Summon, ring" .)

I've seen this clue in the Evening Standard.

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