The most common and most likely answer to this crossword clue is the 10 letter word PIGEONHOLE
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More clues leading to the result PIGEONHOLE
Buddy explains!

The straight part
We know that "box" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case box = pigeonhole.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PIGEONHOLE mean?
PIGEONHOLE noun- One of an array of compartments for housing pigeons.
- One of an array of compartments for receiving mail and other messages at a college, office, etc.
- One of an array of compartments for storing scrolls at a library.
- A similar compartment in a desk, used for sorting and storing papers.
- To categorize; especially to limit or be limited to a particular category, role, etc.
- To put aside, to not act on (proposals, suggestions, advice).