No offence perhaps but one goes to court for it (5,6)

I believe the answer is:

legal action

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'one goes to court for it' is the definition.
I can't tell whether this defines the answer.

'no offence perhaps' is the wordplay.
'no' becomes 'legal' (I can't explain this - if you can you should give a lot more credence to this answer).
'offence perhaps' becomes 'action' (offence is a kind of action).
'legal'+'action'='LEGAL ACTION'

'but' acts as a link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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