The situation in Paris for a mathematician (7)
I believe the answer is:
laplace
'mathematician' is the definition.
(I know this)
'the situation in paris for a' is the wordplay.
I cannot quite understand how this works, but
'situation' could be 'place' (synonyms) and 'place' is present in the answer.
'a' is present in the answer.
A single letter 'l' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
(Other definitions for laplace that I've seen before include "Pierre-Simon -, Fr. mathematician, astronomer" , "French astronomer and mathematician" , "French scientist" .)