Sure you won't have any (5)
I believe the answer is:
doubt
'sure you' is the definition.
The definition suggests a singular noun which matches the answer.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for doubt that I've seen before include "Uncertainty, unsureness" , "Distrust" , "One certainly can't have it" , "Question the truth or accuracy of" , "Hesitate to believe" .)