Stage signals from reported waiting lines (4)
I believe the answer is:
cues
'stage signals' is the definition.
(I've seen this in another clue)
'reported waiting lines' is the wordplay.
'reported' indicates a 'sounds like' (homophone) clue.
'waiting lines' becomes 'queues' ('queue' can be a synonym of 'waiting line').
'queues' sounds like 'CUES'.
'from' is the link.
(Other definitions for cues that I've seen before include "Snooker rods" , "Actors' signals" , "Snooker ball strikers" , "Prompts for action" , "Signals for action" .)