Funny source of bile, sir (7)
I believe the answer is:
risible
'funny' is the definition.
('risible' can be a synonym of 'funny')
'source of bile sir' is the wordplay.
'source of' indicates anagramming the letters.
'bile'+'sir'='bilesir'
'bilesir' with letters rearranged gives 'RISIBLE'.
(Other definitions for risible that I've seen before include "Funny - not even funny" , "Farcical" , "Ludicrous, laughable" , "Absurd" , "Causing laughter - beyond a joke" .)