Possible Clues:

• Opera by Mozart
• Title king in a Mozart opera
• Mozart opera
• I rabbit on initially about people in opera
• Mozart opera about a Cretan king
• One finished nothing after taking in this writer's opera
• Setter treats himself to new beginning in opera
• I make people come in the end to old opera
• Mozart opera; one I demo (anag.)
• Indication European's to appear in one act opera