Dispel the doubts of (6)
I believe the answer is:
assure
'dispel the doubts of' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for assure that I've seen before include "Convince, promise" , "Impart confidence" , "Make sure, guarantee" , "Tell positively" , "Guarantee, promise" .)