US agents have set about making division (4)

I believe the answer is:

gmen

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'us agents' is the definition.
'gmen' can be an answer for 'agents' (G-Man can mean a US federal agent). I'm unsure of the 'us' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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