Possible Clues:

• Used by police against rioters, irritates eyes
• Riot remedy
• It's enough to make you cry
• Riot police may use this eye irritant
• Stuff that irritates eyes, used to subdue riots
• Discharge sprayed by riot police
• Airlike substance that irritates the eyes, used in riots
• Grates a mixture that makes one's eyes water
• It's seen as great in a riot
• Nonlethal weapon