Leave a recalcitrant leader in office (6)
I believe the answer is:
depart
'leave' is the definition.
(synonyms)
'a recalcitrant leader in office' is the wordplay.
'leader' suggests taking the first letters.
'in' means one lot of letters goes inside another.
'office' becomes 'dept'.
The initial letter of 'recalcitrant' is 'r'.
'a'+'r'='ar'
'ar' placed inside 'dept' is 'DEPART'.
(Other definitions for depart that I've seen before include "Retire from" , "Leave (6)" , "Petard (anag.)" , "make tracks" , "Prated (anag.)" .)