There's no longer a tree to be found in the city (6)
I believe the answer is:
'the city' is the definition.
(Exeter is an English city)
'there's no longer a tree to be' is the wordplay.
'there's' is a charade indicator (letters next to each other).
'no longer' becomes 'ex' (prefix meaning former or onetime).
'to be' indicates an anagram.
'tree' with letters rearranged gives 'eter'.
'ex' put next to 'eter' is 'EXETER'.
'found in' acts as a link.
(Other definitions for exeter that I've seen before include "Cathedral city of southwest England" , "SW county town" , "County town and cathedral city of Devon" , "West Country cathedral city" , "See" .)