Understood Sun altered useless articles by newsman (8)
I believe the answer is:
unstated
'understood' is the definition.
(I've seen this before)
'sun altered useless articles by newsman' is the wordplay.
'altered' indicates anagramming the letters.
'useless articles' becomes 'tat' (tat can mean worthless items).
'by' is a charade indicator (letters next to each other).
'newsman' becomes 'ed' (short for editor).
'sun' anagrammed gives 'uns'.
'uns'+'tat'+'ed'='UNSTATED'
(Other definitions for unstated that I've seen before include "taken for granted" , "Not said" , "Not declared" , "kept silent" , "understood" .)