Container to carry forward (6)
I believe the answer is:
carton
'container' is the definition.
(I know that carton is a type of box)
'carry forward' is the wordplay.
'carry' becomes 'cart' (carting is a kind of carrying).
'forward' becomes 'on'.
'cart'+'on'='CARTON'
'to' acts as a link.
(Other definitions for carton that I've seen before include "He did a far, far better thing" , "Light cardboard box" , "Dickensian hero" , "A cardboard container as for milk" , "Flapped cardboard box" .)