Possible Clues:

• Issue that's no longer worth debating
• Fresh motion, top thing to get debated
• It's academic
• Opt motion? That remains to be debated
• It's debatable
• It no longer matters
• It's open to debate
• Option Tom exercised, it�s subject open to debate
• Low temperature below which vessel gets cool causing controversy
• Low temperature affected Pinot? Bone of contention