Gang of criminals send a city wild (9)
I believe the answer is:
syndicate
'gang of criminals' is the definition.
(a criminal syndicate)
'send a city wild' is the wordplay.
'wild' indicates anagramming the letters.
'send'+'a'+'city'='sendacity'
'sendacity' is an anagram of 'SYNDICATE'.
(Other definitions for syndicate that I've seen before include "Team" , "Nay, edicts changed for the business association" , "Organised group of individuals" , "Group of promoters with a common interest" , "Publish simultaneously in a number of newspapers" .)