Alters ridiculous demands, removes source of doubt (6)
I believe the answer is:
amends
'alters' is the definition.
(amending is a kind of altering)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for amends that I've seen before include "Fixes" , "Atonement" , "Makes changes, to a text say" , "Corrects" , "Make them to compensate" .)