Related Clues:

• Take charge
• Pinch-hit
• Enter, as a room
• Try to mediate, perhaps
• Act as a go-between
• Settle disputes
• Conciliate
• Get involved
• Arbitrate
• Do more than mediate
• Get involved with someone else's business
• Act the go-between
• Talk to two 2-Down, say
• Shoe without laces, e.g.
• Oversee negotiations