Offensively impolite (4)
I believe the answer is:
rude
'offensively impolite' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rude that I've seen before include "Impudent" , "Primitive; impolite" , "having no manners?" , "Uncivil" , "Coarse, unpolished" .)