One denouncing a druggie injecting small amount (7)
I believe the answer is:
accuser
'one denouncing' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'a druggie injecting small amount' is the wordplay.
'druggie' becomes 'user' (I've seen this before).
'injecting' indicates putting letters inside.
'small amount' becomes 'cc'.
'a'+'user'='auser'
'auser' going around 'cc' is 'ACCUSER'.
Can you help me to learn more?
(Other definitions for accuser that I've seen before include "One making allegation" , "One to point the finger" , "One who blames" , "I may charge" , "Person bringing charges" .)