Altered lines not disrespectful (8)
I believe the answer is:
insolent
'disrespectful' is the definition.
(similar in meaning)
'altered lines not' is the wordplay.
'altered' indicates anagramming the letters.
'lines'+'not'='linesnot'
'linesnot' with letters rearranged gives 'INSOLENT'.
(Other definitions for insolent that I've seen before include "Rudely disrespectful" , "Rude and disrespectful" , "Pert" , "Extremely fresh" , "Brash" .)