Possible Clues:

• Grain thresher
• Don't pass round the trainee's weapon!
• Old tool for threshing grain
• Threshing tool requiring a natural ability to change hands at the end
• Bomb around large weapon
• Weapon; swing wildly
• Wave (one's arms) about
• One way to attract a lifeguard
• Beat learner driver involved in crash
• Wave about wildly