Ban expert writer (9)
I believe the answer is:
proscribe
'ban' is the definition.
(thesaurus)
'expert writer' is the wordplay.
'expert' becomes 'pro' (I've seen this before).
'writer' becomes 'scribe' (scribe is a kind of writer**).
'pro'+'scribe'='PROSCRIBE'
(Other definitions for proscribe that I've seen before include "Ban" , "Exile" , "Prohibit" , "Denounce" , "Forbid; condemn" .)