Lines once displayed rudeness (9)
I believe the answer is:
insolence
'rudeness' is the definition.
(I know that insolence is a type of rudeness)
'lines once displayed' is the wordplay.
'displayed' indicates an anagram (letters displayed in another way).
'lines'+'once'='linesonce'
'linesonce' with letters rearranged gives 'INSOLENCE'.
(Other definitions for insolence that I've seen before include "Rude behaviour" , "Cheek, irreverence" , "Lip; cheek" , "Rudeness, disrespect" , "lack of respect" .)