Collateral damage done to city user (8)
I believe the answer is:
security
'collateral' is the definition.
(I've seen this before)
'damage done to city user' is the wordplay.
'damage done to' indicates anagramming the letters.
'city'+'user'='cityuser'
'cityuser' is an anagram of 'SECURITY'.
(Other definitions for security that I've seen before include "Protection from damage" , "Safety; stock certificate" , "Safety measures" , "State of being free from danger or injury" , "Refuge" .)