Leave aristocrat behind Stoke's outskirts (3,3)
I believe the answer is:
set off
'leave' is the definition.
(set off can mean to depart)
'aristocrat behind stoke's outskirts' is the wordplay.
'aristocrat' becomes 'toff' (toff can mean an upper-class person).
'behind' is a charade indicator (letters next to each other).
'outskirts' means to remove the middle letters (I've seen 'outskirts of' mean this).
'stoke' with its centre removed is 'se'.
'toff' put after 'se' is 'SET-OFF'.
(Other definitions for set off that I've seen before include "Commence journey or detonate" , "show to advantage" , "'Leave on a journey (3,3)'" , "Begin journey or detonate bomb" , "Display - mount - start journey" .)