Unfortunately smellier, a French city (9)
I believe the answer is:
marseille
'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).
'smellier'+'a'='smelliera'
'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" .)