With a new clue I'd find the mathematician (6)
I believe the answer is:
euclid
'the mathematician' is the definition.
(Euclid is an example)
'with a new clue i'd' is the wordplay.
'with' means one lot of letters go next to another.
'a new' indicates an anagram.
'clue' with letters rearranged gives 'eucl'.
'eucl' put next to 'id' is 'EUCLID'.
'find' is the link.
(Other definitions for euclid that I've seen before include "Alexandrian mathematician" , "Greek mathematician c. three hundred BC" , "Greek mathematician, 3rd century BC" , "Greek geometer" , "Old mathematician" .)