Justified conflict with diatribe by journo (9)
I believe the answer is:
warranted
'justified' is the definition.
('warrant' can be a synonym of 'justify')
'conflict with diatribe by journo' is the wordplay.
'conflict' becomes 'war' (war is a kind of conflict).
'with' is a charade indicator (letters next to each other).
'diatribe' becomes 'rant' (I've seen this in other clues).
'by' says to put letters next to each other.
'journo' becomes 'ed' (I've seen this in other clues).
'war'+'rant'+'ed'='WARRANTED'
(Another definition for warranted that I've seen is " Justified or guaranteed".)