Hard stuff (5)
I believe the answer is:
booze
'hard stuff' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for booze that I've seen before include "Drink too much (colloq.)" , "Drink to excess (colloq.)" , "sauce" , "Alcohol (sl.)" , "plonk?" .)