The most common and most likely answer to this crossword clue is the 3 plus 2 plus 3 letter word ONE ON ONE
I've seen this crossword clue in The Times
O
N
E
O
N
O
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Buddy explains!
The straight part
We know that "No other person present /in the form of 11" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case no other person present /in the form of 11 = one on one.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 ONE ON ONE mean?
ONE ON ONE noun- A contest involving only one player on each side, especially of an activity often involving teams.
- Involving direct communication between two people.
- Involving one attacker and one defender
- Bijective or injective