Unfortunately smellier, a French city (9)
I believe the answer is:
'french city' is the definition.
(I've seen this before)
'unfortunately smellier a' is the wordplay.
'unfortunately' indicates anagramming the letters (a bad or unfortunate spelling).
'smelliera' is an anagram of 'MARSEILLE'.
(Other definitions for marseille that I've seen before include "French port" , "Port city of France" , "fabric" , "French city" , "Major seaport of Southern France" .)