Possible Clues:

• Unseemly male exploit's begin­ning behind the scenes
• Not visible to the audience
• Poor toff's decline unseen by spectators
• What's not seen in main part of house?
• Not seen by the theater audience
• Incorrect point not obvious to audience
• Like many lines fed to actors
• No longer acting, having left old coach
• From the wings of a theatre?
• Old very loud male beginning to expostulate in the wings