Slap for lacking manners (5)
I believe the answer is:
lippy
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for lippy that I've seen before include "Insolent - make-up item" , "Cheeky - cosmetic (informal)" , "Fresh" , "Impertinent" , "item in handbag?" .)