Go to and fro aboard carrier (5)
I believe the answer is:
wagon
'carrier' is the definition.
(a wagon is used to carry things)
'go to and fro aboard' is the wordplay.
'go to and fro' becomes 'wag' (as in a wagging tail).
'aboard' becomes 'on'.
'wag'+'on'='WAGON'
(Other definitions for wagon that I've seen before include "Horse-drawn vehicle" , "Transport" , "Wheeled vehicle drawn by a horse" , "Van, lorry" , "Vehicle for transporting goods" .)