Coach’s posture (8)
I believe the answer is:
carriage
I believe this clue is a double definition.
'coach's' is the first definition.
(synonyms)
'posture' is the second definition.
(I know that posture can be written as carriage)
(Other definitions for carriage that I've seen before include "Railcar or horse-drawn vehicle" , "Posture or train compartment" , "Conveyance (of items of merchandise)" , "Comportment" , "Posture; conveyance" .)