Did you pen best composition? Absolutely! (6,7)

I believe the answer is:

beyond dispute

'absolutely' is the definition.

'did you pen best composition?' is the wordplay.
'composition?' is an anagram indicator (I've seen 'composition' mean this).
'did'+'you'+'pen'+'best'='didyoupenbest'
'didyoupenbest' anagrammed gives 'BEYOND DISPUTE'.

I've seen this clue in The Guardian.

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