The most common and most likely answer to this crossword clue is the 9 letter word SEXTUPLET
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More clues leading to the result SEXTUPLET
Buddy explains!

The straight part
We know that "one of six" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one of six = sextuplet.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 SEXTUPLET mean?
SEXTUPLET noun- A group of six objects.
- One of a group of six persons or animals born from the same mother during the same birth.
- A group of six notes played in the time of four.