If he can’t, I could become clan leader (9)
I believe the answer is:
'clan leader' is the definition.
(I've seen this before)
'if he can't i could become' is the wordplay.
'could become' indicates anagramming the letters.
'ifhecanti' anagrammed gives 'CHIEFTAIN'.
(Other definitions for chieftain that I've seen before include "Head of a clan" , "Head of tribe" , "Clan leader" , "Tribal chief" , "Tribe's leader" .)