It's the done thing in France (4,8)

I believe the answer is:

fait accompli

I'm a little stuck... Click here to teach me more about this clue!

'thing in france' is the definition.
'fait accompli' can be an answer for 'thing' (thesaurus). I am not sure about the 'in france' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

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

I've seen this clue in The Globe and Mail.

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