Rash man’s stolen stimulant (7)
I believe the answer is:
hotspur
'rash man's' is the definition.
(archaic term for a reckless person)
'stolen stimulant' is the wordplay.
'stolen' becomes 'hot' (stolen goods are 'hot').
'stimulant' becomes 'spur' (a spur stimulates or spurs someone on).
'hot'+'spur'='HOTSPUR'
(Other definitions for hotspur that I've seen before include "Percy's name (H.IV Pt.1)" , "named in London team?" , "Impetuous, fiery person - nickname for Henry Percy" , "Sir Henry Percy's name" , "Nickname of Sir Henry Percy (Henry IV, Part one)" .)