Old agreement from very early times (3)
I believe the answer is:
yea
'old agreement' is the definition.
'from very early times' is the wordplay.
'from' indicates a hidden word.
'YEA' is hidden within 'very early times'.
(Other definitions for yea that I've seen before include "MP's 'Yes' vote" , "Yes (archaic)" , "Aye; aye (anag.)" , "Approval" , "'She loves you, ... ... ...' (The Beatles)" .)