Saw a daughter grow old (5)
I believe the answer is:
adage
'saw' is the definition.
('adage' can be a synonym of 'saw')
'a daughter grow old' is the wordplay.
'a daughter' becomes 'ad' (I've seen this in other clues).
'grow old' becomes 'age' ('age' can be a synonym of 'grow old').
'ad'+'age'='ADAGE'
(Other definitions for adage that I've seen before include "True proverb or saying" , "Axiom" , "Dictum" , "Saw, proverb" , "Proverb, maxim" .)