Sin city (5)
I believe the answer is:
sodom
'sin city' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sodom that I've seen before include "Corrupt biblical city" , "Wicked town of ancient Palestine, twinned with Gomorrah" , "With Gomorrah, it was destroyed for wickedness" , "City fired" , "Bad city" .)