Established peace, banishing monsieur from a French region (9)

I believe the answer is:

provencal

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'a french region' is the definition.
(I've seen this before)

'established peace' is the wordplay.
'established' becomes 'proven' (similar in meaning).
'peace' becomes 'cal' (I can't explain this - if you can you should give a lot more credence to this answer).
'proven'+'cal'='PROVENCAL'

'banishing monsieur from' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for provencal that I've seen before include "French language" , "dialect" , "French region" , "of Langue d'oc" , "Language in France" .)

I've seen this clue in The Guardian.

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