Lines up (6)
I believe the answer is:
queues
'lines up' is the definition.
('queue' can be a synonym of 'line up')
This is the entire clue.
(Other definitions for queues that I've seen before include "Lines of waiting people or vehicles" , "Lines of waiters" , "Waits in line" , "lots of waiters" , "Line of waiting people or vehicles" .)