Writer could become Trump's oracle (6,6)
I believe the answer is:
'writer' is the definition.
(Marcel Proust is an example)
'become trump's oracle' is the wordplay.
'become' indicates anagramming the letters.
'trumpsoracle' anagrammed gives 'MARCEL PROUST'.
'could' is the link.
(Other definitions for marcel proust that I've seen before include "novelist" , "Corrupt males (anag) -- French author" .)