Have reservations, but do anyway (5)
I believe the answer is:
doubt
'have reservations' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for doubt that I've seen before include "Have reservations or be uncertain about" , "Be uncertain about or consider unlikely" , "Suspicion" , "Uncertainty about the truth" , "Distrust" .)