Identification adopted by current leader (9)
I believe the answer is:
president
'leader' is the definition.
(type of leader)
'identification adopted by current' is the wordplay.
'identification' becomes 'ID'.
'adopted by' means one lot of letters goes inside another (I've seen this in other clues).
'current' becomes 'present' (similar in meaning).
'id' put into 'present' is 'PRESIDENT'.
(Other definitions for president that I've seen before include "The elected head of a republic" , "2's official title" , "American leader" , "Cleveland?" , "the boss" .)