Drug-injecting worker in need of dough's a mug (6)
I believe the answer is:
beaker
'a mug' is the definition.
(I've seen this before)
'drug-injecting worker in need of dough's' is the wordplay.
'drug' becomes 'e' (e is another name for ecstasy).
'injecting' is an insertion indicator (inserted letters are injected).
'worker in need of dough' becomes 'baker' (a baker uses dough).
'e' going inside 'baker' is 'BEAKER'.
(Other definitions for beaker that I've seen before include "Flatbottomed drinking cup" , "Glass vessel" , "Plastic mug" , "Large drinking cup" , "Mug - large glass" .)