Disputing remark on profit (10)

I believe the answer is:

gainsaying

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'disputing' is the definition.
('gainsay' can be a synonym of 'dispute')

'remark on profit' is the wordplay.
'remark' becomes 'saying' (I can't explain this - if you can you should believe this answer much more).
'on' is a charade indicator (letters next to each other).
'profit' becomes 'gain' (synonyms).
'saying' after 'gain' is 'GAINSAYING'.

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(Other definitions for gainsaying that I've seen before include "Not agreeing" , "denial" .)

I've seen this clue in The Guardian.

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