She sells speed from a stroller (6)
I believe the answer is:
pusher
'a stroller' is the definition.
('pusher' can be a synonym of 'stroller')
'she sells speed' is the wordplay.
I cannot quite see how this works, but
'she' could be 'sher' and 'sher' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'from' acts as a link.
Can you help me to learn more?
(Other definitions for pusher that I've seen before include "Criminal who sells illegal drugs" , "See 20" , "A seller of drugs on the streets" , "Street seller of illegal drugs" .)