Possible Clues:

• One who pelts another with rocks
• He brutally punishes habitual drug user
• Movies' Spicoli, for one
• Pit remover
• One finding roaches at home?
• Expert, by the way, is a drug taker
• Rock thrower one can't keep off the grass?
• Partly dishonest one remains a potential executioner
• Rioter, maybe
• No rest (anag) — cannabis user