There's room for it where things are all boxed up (6)
I believe the answer is:
locker
'where things are all boxed up' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for locker that I've seen before include "Storage unit for personal possessions" , "Small cupboard for personal use" , "Small securable cupboard" , "Chest on board ship" , "Changing room fixture" .)