Showing an unusual degree of proclivity to be polite (5)

I believe the answer is:

civil

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'be polite' is the definition.
(synonyms)

I don't understand the rest of the clue.

(Other definitions for civil that I've seen before include "(Of law) non-criminal" , "Nonviolent refusal to obey laws" , "Courteously polite" , "Courteous, polite" , "Polite and non-military" .)

I've seen this clue in the Evening Standard.

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