Mum, the agent has turned up the draught regulator (6)
I believe the answer is:
damper
But I can't explain it at all! Could you help me understand?
(Other definitions for damper that I've seen before include "Piano string silencer" , "Control for fire - party-pooper" , "Negative influence - more moist" , "Control of stove - wet blanket" , "Control of air to fire" .)