Nasty smell with unruly part of city (7)
I believe the answer is:
borough
'part of city' is the definition.
(a city may be made up of boroughs)
'nasty smell with unruly' is the wordplay.
I cannot really see how this works, but
'nasty' could be 'rough' (I've seen this before) and 'rough' is located in the answer.
'smell' could be 'bo' (abbreviation for Body Odour) and 'bo' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for borough that I've seen before include "6D 5A [TUBE STATION]" , "Region of London" , "Administrative division of London" , "Administrative area" , "Town with a corporation and special privileges" .)