Police department concerned in accidents (3)

I believe the answer is:

cid

I'm a little stuck... Click here to teach me more about this clue!

'police department' is the definition.
(I've seen this in other clues)

'in accidents' is the wordplay.
'in' says the answer is hidden in the clue.
'CID' is hidden within 'accidents'.

'concerned' is the link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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