Leave Labour leader in charge (4)
I believe the answer is:
flee
'leave' is the definition.
(fleeing is a kind of leaving)
'labour leader in charge' is the wordplay.
'leader' indicates taking the first letters.
'in' indicates putting letters inside.
'charge' becomes 'fee' (fee is a kind of charge**).
The first letter of 'labour' is 'l'.
'l' inserted into 'fee' is 'FLEE'.
(Other definitions for flee that I've seen before include "Run quickly away" , "Cut and run" , "Abscond" , "Turn tail" , "Leave" .)