The most common and most likely answer to this crossword clue is the 10 letter word ARCHIMEDES
I've seen this crossword clue in The Times
A
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More clues leading to the result ARCHIMEDES
- Among cunning old people there’s one mathematician
- Mathematician once corresponded in a matter of law
- Chief ordered demise of Greek mathematician
- Old Greek could be forced to heed racism
- Experimental Greek building structure is broken by old Asian
- Leading setter’s swapped seed for mathematician
- Rang war god about scientist
- Ancient scientist sounded into God
- God outside agreed to create mathematician
- Principled Greek, close to Syriza, agreed to be bound by resolution
Buddy explains!
The straight part
We know that "Mathematician once" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mathematician once = archimedes.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.