Cultured European possesses it (6)
I believe the answer is:
polite
'cultured' is the definition.
('polite' can be a synonym of 'cultured')
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for polite that I've seen before include "Considerate, cultured" , "Having good manners, socially correct" , "Cultured, refined" , "Minding one's p's and q's" , "Not rude" .)