Load, as cargo (4)
I believe the answer is:
stow
'load as cargo' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stow that I've seen before include "Lay up, pack away" , "Keep under hatches" , "Pack or store carefully, luggage perhaps" , "Store away tidily" , "Fill by packing tightly" .)