Stick to five lines (5)
I believe the answer is:
stave
'stick' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stave that I've seen before include "Musical staff" , "Set of lines on which musical notes are written" , "Bar" , "Delay before off" , "Stanza of a poem" .)