Crime, it's clear, ruined US city (7)
I believe the answer is:
larceny
'crime' is the definition.
(larceny is a kind of crime)
'clear ruined us city' is the wordplay.
'ruined' indicates an anagram.
'us city' becomes 'ny' (I've seen this in other clues).
'clear' anagrammed gives 'larce'.
'larce'+'ny'='LARCENY'
'it's' acts as a link.
(Other definitions for larceny that I've seen before include "Theft of personal goods" , "Burglary" , "Criminal activity" , "Robbery" , "crime" .)