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"unaccompanied" is also used as a crossword clue. If that's what you saw, the answer is often solitary (8 letters).
Definitions
without anybody else or anything else
Word origin
From un- + accompanied.
Used in a sentence
“The number of children arriving without a parent at the southern border is expected to surpass the levels during the 2014 unaccompanied minor crisis, according to Customs and Border Protection data obtained by CNN.”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Solo”13 letters
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