Trial meant to break will (9)
I believe the answer is:
testament
'will' is the definition.
(synonyms)
'trial meant to break' is the wordplay.
'trial' becomes 'test' (synonyms).
'to break' indicates anagramming the letters.
'meant' with letters rearranged gives 'ament'.
'test'+'ament'='TESTAMENT'
(Other definitions for testament that I've seen before include "Either of the two main divisions of the Bible" , "Proof" , "Statement about final intentions" , "Will - covenant" , "Earnest" .)