Does one's bit for detective initially captured in article associated with wrongdoing (7,2)

I believe the answer is:

pitches in

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'does' is the definition.
Although both the answer and definition are verbs in their -s form, I don't see how they can define each other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Another definition for pitches in that I've seen is " Co-operates enthusiastically".)

I've seen this clue in The Irish Times.

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