Taking action when one is cheating (5)

I believe the answer is:

doing

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This clue could be a double definition.

'taking action' is the first definition.
'doing' can be an answer for 'action' (doing is a kind of action). I'm unsure of the 'taking' bit.

'one is cheating' is the second definition.
('do' can mean to scam or con someone)

'when' acts as a link.

Can you help me to learn more?

(Other definitions for doing that I've seen before include "Effecting" , "visiting as a tourist" , "Execution" , "deed?" , "Performing a task" .)

I've seen this clue in the Evening Standard.

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