Make love with fellow, American idiot (6)
I believe the answer is:
doofus
'idiot' is the definition.
(both can mean a foolish person)
'make love with fellow american' is the wordplay.
'make' becomes 'do' (do can mean to make or prepare).
'love' becomes 'o' (love means zero in tennis).
'with' says to put letters next to each other.
'fellow' becomes 'f' (abbreviation - of a society etc.).
'american' becomes 'US' (United States).
'do'+'o'+'f'+'us'='DOOFUS'
(Other definitions for doofus that I've seen before include "American fool - US food (anag)" , "Nitwit" .)