Curfew
The required end time for amplified music or the event, set by the venue, permit, local rules, or show agreement.
In practice
Treat curfew as a fixed point in the running order and confirm whether it applies to the performance, amplified sound, or the event as a whole. The advance should record the agreed time and who needs to know if a schedule delay puts it at risk. Fees or other consequences depend on the venue terms and local requirements.