Man of principle made riches in a way (10)
I believe the answer is:
archimedes
'man of principle' is the definition.
(I've seen this before)
'made riches in a way' is the wordplay.
'in a way' is an anagram indicator.
'made'+'riches'='maderiches'
'maderiches' with letters rearranged gives 'ARCHIMEDES'.
(Other definitions for archimedes that I've seen before include "Old mathematician" , "'Eureka' scientist" , "Greek physicist" , "Greek mathematician and inventor" , "Greek mathematician ('Eureka')" .)