A character in Greek chorus is hilarious (7)
I believe the answer is:
amusing
'hilarious' is the definition.
(thesaurus)
'a character in greek chorus' is the wordplay.
'a character in greek' becomes 'amu' (I can't explain this - if you can you should believe this answer much more).
'chorus' becomes 'sing' (to chorus is to sing in chorus).
'amu'+'sing'='AMUSING'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for amusing that I've seen before include "Pleasantly entertaining" , "Entertaining in a mild way" , "Entertaining, pleasing" , "Droll" , "Pleasantly diverting" .)