One-time striker apparently losing weight without drug (9)
I believe the answer is:
lightning
'drug' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for lightning that I've seen before include "Discharge of electricity in the atmosphere" , "Atmospheric discharge" , "Atmospheric electricity" , "Natural discharge of electricity" , "Flash in the sky" .)