Guff (3)
I think it could be either:
'guff' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lip that I've seen before include "Rim; impudence (slang)" , "Sauce" , "Edge, rim" , "Rim; impertinence" , "Rim of an orifice" .)
'guff' is the definition.
(I know that guff can be written as rot)
This is the entire clue.
(Other definitions for rot that I've seen before include "'Decay, decompose (3)'" , "SECOND PART OF 25" , "Decompose; rubbish" , "Deterioration" , "Balderdash" .)