Funny business with amended claim (7)
I believe the answer is:
comical
'funny' is the definition.
('comical' can be a synonym of 'funny')
'business with amended claim' is the wordplay.
'business' becomes 'co'.
'with' is a charade indicator (letters next to each other).
'amended' indicates an anagram.
'claim' anagrammed gives 'mical'.
'co'+'mical'='COMICAL'
(Other definitions for comical that I've seen before include "Witty" , "priceless" , "Amusing or droll" , "Humorous" , "Rich" .)