The most common and most likely answer to this crossword clue is the 10 letter word PROSTHESIS
I've seen this crossword clue in The Guardian
P
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S
T
H
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S
More clues leading to the result PROSTHESIS
- Expert's treatise shows what can help a handicapped person
- Dissertation from expert, not an original member?
- Artificial part of expert’s argument
- Substitute part of body of academic work by many 13
- Medical substitute aces academic assignment
- Article sister attached to former F1 champ missing extremity?
- False part of argument by those in favour
- What Paralympian may have –- he is involved with sports
- Pirate ship stores wooden leg perhaps
- Dodgy hip, so rests getting replacement part?
Buddy explains!

The straight part
We know that "False part" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case false part = prosthesis.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 PROSTHESIS mean?
PROSTHESIS noun- An artificial replacement for a body part, either internal or external.
- Prothesis.