Checkout annoyance (4)
'checkout annoyance' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for line that I've seen before include "column" , "Phone connection; queue" , "short note" , "business" , "Some poetic feet; boundary, when drawn" .)
(Other definitions for wait that I've seen before include "singer" , "Delay, stand by" , "Watchman" , "Hold on" , "Period of delay" .)