Quaintly charming being in school detention (4)

I believe the answer is:

olde

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'quaintly charming' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'in school detention' is the wordplay.
'in' says the answer is hidden in the clue.
'OLDE' is hidden within 'school detention'.

'being' is the link.

Can you help me to learn more?

I've seen this clue in The Guardian.

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