Drinks purchasing right drinks (6)
I believe the answer is:
shorts
'drinks' is the definition.
'drinks purchasing right' is the wordplay.
'drinks' becomes 'shots' (alcoholic drinks).
'purchasing' is an insertion indicator (some letters take possession of others).
'right' becomes 'r' (common abbreviation).
'shots' enclosing 'r' is 'SHORTS'.
(Other definitions for shorts that I've seen before include "Reduced trousers" , "Item of clothing; drinks of spirit" , "Cut-off trousers" , "Summer trousers" , "Trousers that end at or above the knee" .)