Fool starts to assess sensitive situation (3)
I believe the answer is:
ass
'fool' is the definition.
(both can mean a stupid person)
'starts to assess sensitive situation' is the wordplay.
'starts to' indicates taking the first letters.
The first letters of 'assess sensitive situation' is 'ASS'.
(Other definitions for ass that I've seen before include "Donkey or foolish person" , "Horse-type animal" , "Titania loved one" , "Animal of horse family" , "Quadruped; fool" .)