Idiotic person who's seen to have change of heart (7)
I believe the answer is:
witless
'idiotic' is the definition.
(thesaurus)
'person who's seen to have change of heart' is the wordplay.
I cannot really understand how this works, but
'person' could be 'wit' (wit is a kind of person) and 'wit' is located in the answer.
The remaining letters 'less' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for witless that I've seen before include "Daft" , "Out of one's mind (maybe scared)" , "Lacking sense, understanding or judgment" , "Foolish, stupid" .)