Firm dad keeping quiet in officers' HQ (3,4)

I believe the answer is:

cop shop

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'officers' hq' is the definition.
I know nothing about this answer so I can't judge whether this works.

'firm dad keeping quiet' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'dad' becomes 'pop' (synonyms).
'keeping' indicates putting letters inside (some letters kept inside).
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'pop' going around 'sh' is 'pshop'.
'co'+'pshop'='COP-SHOP'

'in' is the link.

Can you help me to learn more?

(Other definitions for cop shop that I've seen before include "Nick" , "'Police station (3,4)'" , "Police station (slang)" , "office investigating crime" .)

I've seen this clue in The Guardian.

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