Lines (up) (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
queues
'lines up' is the definition.
('queue' can be a synonym of 'line up')
This is all the 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" .)