Eight lines of verse (6)
I believe the answer is:
octave
'eight lines of verse' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for octave that I've seen before include "Series of eight consecutive musical notes" , "Eight-note range" , "Span of eight notes" , "Interval of 12 semitones" , "Interval from one C to the next C" .)