The most common and most likely answer to this crossword clue is the 5 letter word EULER
I've seen this crossword clue in Financial Times
E
U
L
E
R
More clues leading to the result EULER
- An irrational king executed a mathematician
- Mathematician showing odd parts equalled four, finally
- Turn to write another hint for solvers missing Celsius for scientist
- Mathematician showing hesitation about principle that's not right
- English monarch beheaded calculating Swiss
- Sacré bleu! Wrong cab’s gone off for mathematician
- Mathematician/engineer looking for regularity in equal gears
- The French in their way rejected Swiss scientist
- Well-spoken mathematician
- Euclid’s first rule confounded by mathematician
Buddy explains!
The straight part
We know that "Swiss scientist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swiss scientist = euler.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.