Crossword Genius

At the Sorbonne, it’s the done thing (4,8)

Ross

I believe the answer is:

fait accompli

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'thing' is the definition.
(thesaurus)

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(Other definitions for fait accompli that I've seen before include "A done deal" , "Irreversible action" , "Something irreversibly decided" , "Something done and unalterable" , "Irreversible act" .)

I've seen this clue in The Sunday Times.
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