Saw lawyer in time (5)
I believe the answer is:
adage
'saw' is the definition.
(saw can mean a proverb or saying)
'lawyer in time' is the wordplay.
'lawyer' becomes 'da' (district attorney).
'in' indicates putting letters inside.
'time' becomes 'age' (an age is a period of time).
'da' put into 'age' is 'ADAGE'.
(Other definitions for adage that I've seen before include "Wise old saying" , "Slogan" , "Proverb expressing a general truth" , "Axiom" , "Old saw" .)