Circular tour where Saudi jewel thief ends up (5)
I believe the answer is:
flier
'circular' is the definition.
('flier' can be a synonym of 'circular')
'tour where saudi jewel thief ends up' is the wordplay.
'ends' indicates one should take the final letters.
'up' says the letters should be written backwards (in down clue: letters go upwards).
The last letters of 'tour where saudi jewel thief' are 'reilf'.
'reilf' reversed gives 'FLIER'.
(Other definitions for flier that I've seen before include "Good start" , "Turkey perhaps?" , "PO, for example" , "Advertisement" , "Rifle for airman" .)