Crossword Genius

The detectives decided, indeed! (3)

Ross

I believe the answer is:

cid

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

'the detectives' is the definition.
(abbreviation for Criminal Investigation Department)

'decided indeed' is the wordplay.
'CID' is hidden within the letters.
But, I'm unsure how the hidden word is indicated.

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