Disputed titles will contain duty, providing definitive trial (6,4)
I believe the answer is:
litmus test
'definitive trial' is the definition.
(a litmus test is a decisive or definitive test)
'disputed titles will contain duty' is the wordplay.
'disputed' is an anagram indicator.
'will contain' means one lot of letters goes inside another.
'duty' becomes 'must' (something you must do).
'titles' anagrammed gives 'litest'.
'litest' placed around 'must' is 'LITMUS TEST'.
'providing' acts as a link.
(Other definitions for litmus test that I've seen before include "Observer may see red after one" , "Chemical trial" .)