Booking in doubt? (11)
I believe the answer is:
reservation
I believe this clue is a double definition.
'booking' is the first definition.
(I know that booking can be written as reservation)
'doubt?' is the second definition.
(to have reservations is to have doubts)
'in' acts as a link.
(Other definitions for reservation that I've seen before include "Qualification, proviso" , "Booking (in a restaurant)" , "Putting aside" , "Expression of doubt (about a claim)" , "misgiving" .)