Ignorant nitwit shot with gun (9)
I believe the answer is:
unwitting
'ignorant' is the definition.
(I know that ignorant can be written as unwitting)
'nitwit shot with gun' is the wordplay.
'shot with' indicates anagramming the letters.
'nitwit' anagrammed with 'gun' gives 'UNWITTING'.
(Other definitions for unwitting that I've seen before include "Not done with purpose or intent" , "not conscious" , "Innocent" , "Unknowing" .)