Possible Clues:

• That's the very last thing you'd expect from 15 across, by the sound of it
• One might perhaps, have a penchant for this at last
• The sort of 23 down that's the last thing you'd expect from the bird
• Final utterance
• Last act or work, as of noble bird
• Gloria, famous last words of?
• Actress Gloria has good final performance
• New boy in Loot's final performance
• Bird music for last act before death or retirement
• Last act of Shakespeare over - good