The most common and most likely answer to this crossword clue is the 7 letter word PACKING
I've seen this crossword clue in Financial Times
P
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Buddy explains!
The straight part
We know that "How one may be sent off/boxing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case how one may be sent off/boxing = packing.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 PACKING mean?
PACKING verb- (physical) To put or bring things together in a limited or confined space, especially for storage or transport.
- (social) To cheat.
- To load with a pack
- To load; to encumber.
- To move, send or carry.
- To block a shot, especially in basketball.
- (of the forwards in a rugby team) To play together cohesively, specially with reference to their technique in the scrum.
- (of a drag king, transman, etc.) To wear a prosthetic penis inside one’s trousers for better verisimilitude.
- The action of the verb.
- As a concrete noun.