ULEZ boundaries backed by prosperous financial centre (6)
I believe the answer is:
zurich
'financial centre' is the definition.
(Zurich is an important financial city)
'ulez boundaries backed by prosperous' is the wordplay.
'boundaries' says to hollow out the word (remove centre letters) (only the edge or boundary letters remain).
'backed' says the letters should be written in reverse.
'by' is a charade indicator (letters next to each other).
'prosperous' becomes 'rich' (similar in meaning).
'ulez' with its centre removed is 'uz'.
'uz' backwards is 'zu'.
'zu'+'rich'='ZURICH'
(Other definitions for zurich that I've seen before include "Swiss financial centre" , "Largest Swiss city" , "See 8" , "Swiss financial capital" , "Swiss city noted for gnomes" .)