Doubting (9)
I believe the answer is:
sceptical
'doubting' is the definition.
(I know that doubting can be written as sceptical)
This is all the clue.
(Other definitions for sceptical that I've seen before include "Inclined not to believe" , "Inclined to doubt accepted opinions" , "Given to doubt" , "dubious" , "Disinclined to believe" .)