A man of principle (5)
I believe the answer is:
maxim
I believe this is a double definition.
'a man' is the first definition.
'principle' is the second definition.
(I've seen this in another clue)
'of' is the link.
(Other definitions for maxim that I've seen before include "Widely accepted saying" , "Pithy statement of a general truth" , "General rule" , "Saying, adage" , "Saw - type of gun" .)