Drug behind endless corruption in city (9)
I believe the answer is:
edinburgh
'city' is the definition.
(Edinburgh is an example)
'drug behind endless corruption' is the wordplay.
'endless' means to remove the last letter.
'corruption' indicates an anagram.
'drug'+'behind'='drugbehind'
'drugbehind' with its last letter taken away is 'drugbehin'.
'drugbehin' with letters rearranged gives 'EDINBURGH'.
'in' is the link.
(Other definitions for edinburgh that I've seen before include "fringe city" , "Scotland's capital" , "Capital city of Scotland" , "City on the Firth of Forth" , "Lothian city" .)