This one was tricky to navigate and did, finally, leave them dumbfounded (6)
I believe the answer is:
amazed
'dumbfounded' is the definition.
('amaze' can be a synonym of 'dumbfound')
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for amazed that I've seen before include "Flabbergasted" , "Filled with astonishment" , "Dumbfounded" , "knocked for six" , "Completely surprised" .)