Without a doubt, egghead's trick with bot upset them (2,2,4)
I believe the answer is:
to be sure
'without a doubt' is the definition.
(I've seen this in another clue)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for to be sure that I've seen before include "Undoubtedly" , "I admit" , "Without doubt" , "Of course, certainly" , "Admittedly" .)