Backtalk (3)
'backtalk' is the definition.
(synonyms)
This is all the clue.
(Other definitions for lip that I've seen before include "Insolence (slang)" , "Fleshy fold of mouth tissue" , "Rim; impertinence" , "Top edge of a vessel" , "In slang, impudent talk" .)
'backtalk' is the definition.
(I know that backtalk can be written as sass)
This is the entire clue.
(Another definition for sass that I've seen is " Cheek".)