Adage, dictum (5)
I believe the answer is:
maxim
This clue is a double definition.
'adage' is the first definition.
(I've seen this in another clue)
'dictum' is the second definition.
(thesaurus)
(Other definitions for maxim that I've seen before include "Old machine-gun" , "Short pithy statement" , "Axiom" , "Apophthegm" , "Principle-first machine gun" .)