Party of America supplying dimwit (6)
I believe the answer is:
doofus
'dimwit' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'party of america' is the wordplay.
'party' becomes 'do' (do can informally mean a party).
'america' becomes 'US' (United States).
'do'+'of'+'us'='DOOFUS'
'supplying' acts as a link.
Can you help me to learn more?
(Other definitions for doofus that I've seen before include "Nitwit" , "American fool - US food (anag)" .)