Polite, courteous (5)
I believe the answer is:
civil
I believe this is a double definition.
'polite' is the first definition.
(synonyms)
'courteous' is the second definition.
(I've seen this in another clue)
(Other definitions for civil that I've seen before include "Urbane" , "Not rude" , "Relating to citizens" , "Courteous, polite" , "Courteously polite" .)