Shoot; messenger (6)
I believe the answer is:
runner
I believe this is a double definition.
'shoot' is the first definition.
(plant shoot that goes along the ground)
'messenger' is the second definition.
(someone who carries a message)
(Other definitions for runner that I've seen before include "done by con man, perhaps" , "Participant in a race" , "Horse in a race; shoot" , "Athlete; narrow rug" , "E.g. miler" .)