Be unhappy, perhaps, as tenant’s picked up small revolver (8)
I believe the answer is:
roulette
'small revolver' is the definition.
(a roulette wheel revolves)
I don't understand how the remainder of the clue works.
(Other definitions for roulette that I've seen before include "Wheel of fortune" , "Half of 1D [GAME OR BIRD]" , "Gambling game with small ball and revolving disc (8)" , "Wheel for the gambler" , "Table game" .)