Sass (3)
'sass' is the definition.
(I know that sass can be written as lip)
This is all the clue.
(Other definitions for lip that I've seen before include "Brink" , "In slang, impudent talk" , "Fleshy fold of mouth tissue" , "Brim" , "Edge, rim" .)
(Other definitions for impudence that I've seen before include "Audacity" , "Impertinence, insolence" , "Cheek" , "neck" , "bad manners" .)