Showing bad manners (12)
I believe the answer is:
discourteous
'showing bad manners' is the definition.
(discourteous means impolite or disrespectful)
This is the entire clue.
(Other definitions for discourteous that I've seen before include "Uncouth" , "Impolite" , "Rude, inconsiderate" , "Ill-mannered" .)