Drunk started smoking (3,2)
I believe the answer is:
lit up
I believe this is a double definition.
'drunk' is the first definition.
(I've seen this before)
'started smoking' is the second definition.
(I've seen this in another clue)
(Other definitions for lit up that I've seen before include "Illuminated (by drink or drugs?)" , "high" , "was illuminating" , "Drunk (informal)" , "bulb so transformed room?" .)