Possible Clues:

• Substance used to slow down neutrons in nuclear reactors
• Presiding officer, a Marxist, driven round in car
• One checking discussions conducted fairly
• One who presides over a panel discussion
• Debate runner
• Way bad person gets nothing right — officer to step in?
• Presiding officer’s way with one who deserts other ranks
• Someone who presides over a forum
• Youth on scooter run overtaking Muse and church official?
• Presbyterian minister - superintendent of university examinations