Downgrade area covered by revolutionary writer (7)
I believe the answer is:
cheapen
'downgrade' is the definition.
(thesaurus)
'area covered by revolutionary writer' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'covered by' says to put letters next to each other (on top of in a down clue).
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'writer' becomes 'pen' (I've seen this before).
'a' after 'che' is 'chea'.
'chea'+'pen'='CHEAPEN'
(Other definitions for cheapen that I've seen before include "Degrade (something)" , "Cut" , "decrease in value" , "Debase" , "Reduce the price of" .)