Accepted way of behaving with unknown quantity in French region (8)

I believe the answer is:

normandy

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

I cannot understand how the remainder of the clue works.

(Other definitions for normandy that I've seen before include "Region of northwest France" , "across the sea" , "Region of NW France bordering on English Channel" , "duchy" , "over the water" .)

I've seen this clue in The Telegraph.

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