Possible Clues:

• Royal supremacy stymied, by the sound of it?
• What's the welcoming king on?
• It's definitely a reserved seat
• Where a sovereign sits
• Seat chucked in the auditorium
• Small boy put in the high chair
• WC, colloquially
• John's projected to the audience
• Sovereign's position confused on the radio
• Seat of power from which one's unseated, say