Possible Clues:

• Percussion cap, e.g.
• Setter-off observed climbing a hill
• Device activating explosives
• Spoil a great set-up and this will cause an outburst
• Explosive type laid into privileged Eton — a Tory-hater
• It sets off to give a list of the famous, going back
• Explosive initiator
• Putting up duty list, registered a small charge
• Rejected roster, famous as a cause for explosion
• Ka-boom! maker