Still remaining in force when detaining the righteous (7,4)

I believe the answer is:

holding good

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'still remaining in force' is the definition.
I know nothing about this answer so I can't tell whether this works.

'detaining the righteous' is the wordplay.
'detaining' becomes 'holding' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'the righteous' becomes 'good' (I've seen this before).
'holding'+'good'='HOLDING GOOD'

'when' acts as a link.

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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