Possible Clues:

• Katy did horrible thing - it causes them to drop like flies perhaps
• Camper's need
• Might it create a no-fly zone?
• Pet silencer working fast — that should keep the little pests away
• Solution for a camping problem
• Debugging aid?
• Brainwashed outcast regressing fast flies away with this?
• Causes one to drop like flies perhaps provided Katy did something horrid
• The cause of flies being left undone?
• Citronella, say, I sell with ten percent off