Possible Clues:

• Done deal (French)
• Something already done (French)
• Something done and unalterable
• Fact I complain endlessly about: it's a done deal
• Impact if coal gets abandoned is already decided
• What's done (and cannot be undone)
• Wild acclaim if top becomes a foregone conclusion
• Not showing total belief, partner avoids church as the done thing?
• It's the done thing in France
• Something already decided