Possible Clues:

• Opera in which dog bites priest?
• Rendered smooth-running poem, tipped to become opera
• The one that Beethoven made (see 15-Across)
• Opera about the steadfast wife of a political prisoner
• 'Leonore' was the original title of this Beethoven opera
• Sloshed, I initially fell over in opera
• Opera in which priest is bitten by dog?
• Contrarily put on Grease though opera's wanted
• Work of art showing priest in dog collar
• Opera featuring the 'Prisoners' Chorus'