Cardboard container (6)
'cardboard container' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for carton that I've seen before include "Flapped cardboard box" , "Container for food or liquid" , "Cantor (anag)" , "He did a far, far better thing" , "Small, light box or container" .)
(Other definitions for packet that I've seen before include "Container - ship" , "Mail ship" , "Container; much money" , "Data transmission unit - large sum" , "Paper or cardboard container" .)