Possible Clues:

• Be of service to one stuck in revolting volcanic discharge
• Use a cover for the audience
• Profit from a mask in a manner of speaking
• Helpfulness
• Make use of a sign on the house starting off
• Be of advantage to
• Benefit from a curtain in auditorium
• A disguise said to be useful
• Put to use
• To no __ (in vain)