The most common and most likely answer to this crossword clue is the 10 letter word FRACTIONAL
I've seen this crossword clue in The Daily Telegraph
F
R
A
C
T
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A
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More clues leading to the result FRACTIONAL
Buddy explains!

The straight part
We know that "Part" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case part = fractional.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 FRACTIONAL mean?
FRACTIONAL noun- (grammar) An expression of a fractional number.
- Partial ownership of a property, such as real estate or a chartered airplane, such that each partial owner has use of the property for only a portion of the time.
- Relating to a fraction in a material distillation or separation process.
- Pertaining to a fraction.
- Divided; fragmentary; incomplete.
- Very small; minute.
- Relating to a process or product of fractional distillation.