What does "a turn-away crowd" mean?
Solution 1:
If a venue is sold out, all tickets are sold and there are none left. People arriving too late will be turned away (refused entry).
turn away
Refuse to allow someone to enter or pass through a place:
tourists were turned away at the crossing points[ODO]
A “turn-away crowd” is so large that people are being turned away because no more can be accommodated.