Took weed maybe, not mint (4)
I believe the answer is:
'not mint' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for used that I've seen before include "Accustomed - exploited" , "Was treating" , "Utilised" , "That's not new" , "worked unfairly" .)