Stupid fool going after credit (5)
I believe the answer is:
crass
'stupid' is the definition.
(I've seen this in another clue)
'fool going after credit' is the wordplay.
'fool' becomes 'ass' (both can mean a stupid person).
'going after' says to put letters next to each other.
'credit' becomes 'cr' (abbreviation).
'ass' put after 'cr' is 'CRASS'.
(Other definitions for crass that I've seen before include "Insensitively stupid" , "Indelicate" , "Asinine" , "Totally lacking in sensibility" , "Grossly insensitive" .)