Dealing with nun, an oppositional figure (8)

I believe the answer is:

resister

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'an oppositional figure' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?

'dealing with nun' is the wordplay.
'dealing with' becomes 're' (regarding).
'nun' becomes 'sister' (a nun might be called sister).
're'+'sister'='RESISTER'

Can you help me to learn more?

I've seen this clue in The Telegraph.

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