See to it that you convince beyond doubt (4,4)
I believe the answer is:
make sure
'see to it' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for make sure that I've seen before include "Put beyond doubt" , "Establish beyond doubt, be certain" , "Ascertain" , "Confirm" , "Put beyond risk" .)