Leader's a supporter of independence? (7)
I believe the answer is:
skipper
'leader's' is the definition.
(thesaurus)
'a supporter of independence?' is the wordplay.
'a' becomes 'per'.
'supporter of' says to put letters next to each other (supports the letters above in a down clue).
'independence?' becomes 'skip' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'per' put after 'skip' is 'SKIPPER'.
(Other definitions for skipper that I've seen before include "Captain of team or boat - type of butterfly" , "Shakespeare's giddy youth" , "One who misses" , "girl with rope?" , "team leader" .)