Information about male agents (1-3)

I believe the answer is:

g-men

'agents' is the definition.
(G-man is an example)

'information about male' is the wordplay.
'information' becomes 'gen' (gen is a kind of information).
'about' means one lot of letters goes inside another.
'male' becomes 'm' (common abbreviation).
'gen' enclosing 'm' is 'G-MEN'.

I've seen this clue in The Independent.

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