Ha-ha! A wit convulsed native American leader (8)
I believe the answer is:
hiawatha
'native american leader' is the definition.
The definition suggests a singular noun which matches the answer.
'ha-ha a wit convulsed' is the wordplay.
'convulsed' is an anagram indicator (letters convulse or shake).
'ha'+'ha'+'a'+'wit'='hahaawit'
'hahaawit' with letters rearranged gives 'HIAWATHA'.
Can you help me to learn more?
(Other definitions for hiawatha that I've seen before include "Red Indian hero of Longfellow's poem" , "choice of subject for Longfellow" , "Indian hero of Longfellow's epic poem" , "H. W. Longfellow hero" , "Indian hero of Longfellow's poem 'The Song of ... '" .)