Idiot getting role after change of heart (4)
I believe the answer is:
prat
'idiot' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
(Other definitions for prat that I've seen before include "Wally" , "Stupid person" , "In slang, a fool" , "Incompetent idiot" , "Rapt kind of fool" .)