Courier has difficulty getting green transport (9)
I believe the answer is:
messenger
'courier' is the definition.
('messenger' can be a synonym of 'courier')
'difficulty getting green transport' is the wordplay.
'difficulty' becomes 'mess' (mess is a kind of difficulty**).
'getting' says to put letters next to each other.
'transport' is an anagram indicator (I've seen 'transported' mean this).
'green' is an anagram of 'enger'.
'mess'+'enger'='MESSENGER'
'has' acts as a link.
(Other definitions for messenger that I've seen before include "Kind of bearer - don't shoot him" , "Person carrying information to another" , "Courier - don't shoot him" , "He takes note" , "He brings the news - don't shoot him" .)