Courier, in confusion, turning green (9)
I believe the answer is:
messenger
'courier' is the definition.
(I know that courier can be written as messenger)
'confusion turning green' is the wordplay.
'confusion' becomes 'mess' (mess can mean confusion or chaos).
'turning' indicates anagramming the letters.
'green' is an anagram of 'enger'.
'mess'+'enger'='MESSENGER'
'in' is the link.
(Other definitions for messenger that I've seen before include "He brings the news - don't shoot him" , "Bearer of communication" , "He's just bringing the word - don't shoot him" , "He takes note" , "Runner" .)