A fool occupied by greed, say? That's comical (7)
I believe the answer is:
amusing
'comical' is the definition.
(I've seen this before)
'a fool occupied by greed say?' is the wordplay.
'fool' becomes 'mug' ('mug' can be a synonym of 'fool').
'occupied by' is an insertion indicator.
'greed say?' becomes 'sin' (greed is a kind of sin).
'mug' going around 'sin' is 'musing'.
'a'+'musing'='AMUSING'
'that's' is the link.
(Other definitions for amusing that I've seen before include "Pleasantly entertaining" , "Giving entertainment" , "Mildly funny - diverting" , "Comical" , "Entertaining, pleasing" .)