Mastermind running riot in Greene (8)
I believe the answer is:
engineer
'mastermind running' is the definition.
'engineer' can be an answer for 'mastermind' (both can mean to contrive or plot something). I am unsure of the 'running' bit.
'riot in greene' is the wordplay.
'riot' indicates anagramming the letters.
'in'+'greene'='ingreene'
'ingreene' with letters rearranged gives 'ENGINEER'.
Can you help me to learn more?
(Other definitions for engineer that I've seen before include "Professional who may be civic, electrical or mechanical" , "US or Canadian train driver" , "One uses scientific knowledge to solve practical problems" , "Designer of machines etc" , "Train driver, say" .)