Less polite (5)
I believe the answer is:
ruder
'less polite' is the definition.
('rude' can be the opposite of 'polite' so perhaps 'ruder' is reasonable for 'less polite')
This is all the clue.
(Other definitions for ruder that I've seen before include "More impudent" , "comparatively unsophisticated" , "less pleasant in manner" , "Coarser" , "Less polite" .)