Old saw (5)
'old saw' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for adage that I've seen before include "Dictum" , "Wise old saying" , "Proverb expressing a general truth" , "Old saw" , "Well-remembered proverb or saying" .)
(Other definitions for dated that I've seen before include "Unfashionable" , "No longer fashionable or current" , "Obsolete" , "Out of fashion" , "Rusty" .)