Euler’s number substitutes for zero in arrangement for mathematician (6)

I believe the answer is:

fermat

I'm a little stuck... Click here to teach me more about this clue!

'for mathematician' is the definition.
(Fermat is an example)

I don't understand the remainder of the clue.

(Other definitions for fermat that I've seen before include "he had no room to write down proof" , "French Mathematician (famous last theorem)" , "One with famous last theorem" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app