Often numbered container (3)
I believe the answer is:
box
'container' is the definition.
(I know that box is a type of container)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for box that I've seen before include "Christmas present" , "Wooden case" , "Punch" , "Carton" , "Fight; tree; container" .)