Possible Clues:

• Prankster's weapon
• Kid's weapon
• Blowpipe hit ape's nose
• A blow directed from it quickens the pulse
• There's a "Scram!" when boy's brought round slightly dangerous toy
• Missile launcher? Sound alarm when leading in lord
• Child's 'gun'
• So the opera develops — it sets the pulse racing!
• Weapon to quicken the pulse
• Weapon whose use may make a child's pulse race?