More ill-mannered (5)
I believe the answer is:
ruder
'more ill-mannered' is the definition.
('rude' can be a synonym of 'ill-mannered')
This is all the clue.
(Other definitions for ruder that I've seen before include "Less civil" , "Less polite" , "Coarser" , "More impudent" , "less pleasant in manner" .)