Prim and a little proper with the rather discourteous (7)

I believe the answer is:

prudish

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

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

(Other definitions for prudish that I've seen before include "Prissy" , "not liking anything too hot!" , "Excessively prim" , "Having extreme propriety, easily shocked by sexual matters" , "Having exaggerated propriety, easily shocked" .)

I've seen this clue in the Evening Standard.

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