Drug runner is part of ring in New Orleans, initially (5)
I believe the answer is:
narco
'drug runner' is the definition.
'part of ring in new orleans initially' is the wordplay.
'part of ring' becomes 'arc'.
'in' indicates putting letters inside.
'initially' indicates taking the first letters.
The initial letters of 'new orleans' is 'no'.
'arc' put within 'no' is 'NARCO'.
'is' acts as a link.
(Other definitions for narco that I've seen before include "Drugs agent (US slang)" , "Drug trafficker" , "American drug agent" , "Member of US drugs squad" .)