Ringing dope in factory (8)
I believe the answer is:
plangent
'ringing' is the definition.
('plangent' can be a synonym of 'ringing')
'dope in factory' is the wordplay.
'dope' becomes 'gen' (I've seen this in other clues).
'in' indicates putting letters inside.
'factory' becomes 'plant' (I've seen this before).
'gen' placed within 'plant' is 'PLANGENT'.
(Other definitions for plangent that I've seen before include "Loud and sad" , "Clangorous" , "Noisy" , "information to put around" , "Possibly ringing" .)