After the trial meant to change the will (9)
I believe the answer is:
testament
'the will' is the definition.
(synonyms)
'after the trial meant to change' is the wordplay.
'after' is a charade indicator (letters next to each other).
'the trial' becomes 'test' ('test' can be a synonym of 'trial').
'to change' is an anagram indicator.
'meant' anagrammed gives 'ament'.
'test' next to 'ament' is 'TESTAMENT'.
(Other definitions for testament that I've seen before include "evidence" , "with 1a [NEW] where is Mark?" , "Proof" , "Written statement of wishes" , "Will - part of bible" .)