... drug quietly injected by female (4)
I believe the answer is:
dope
'drug' is the definition.
(colloquial)
'quietly injected by female' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'injected by' means one lot of letters goes inside another (I've seen this in other clues).
'female' becomes 'doe' (female deer).
'p' put inside 'doe' is 'DOPE'.
(Other definitions for dope that I've seen before include "Illegal drugs; fool" , "Dolt -- drug" , "grass, perhaps" , "Fool - cannabis" , "One simple" .)