Devalue revolutionary copy by noon (7)
I believe the answer is:
cheapen
'devalue' is the definition.
(I've seen this in another clue)
'revolutionary copy by noon' is the wordplay.
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'copy' becomes 'ape' (ape can mean to copy or imitate).
'by' says to put letters next to each other.
'noon' becomes 'n' (abbreviation for noon).
'che'+'ape'+'n'='CHEAPEN'
(Other definitions for cheapen that I've seen before include "Debase" , "Reduce the price of" , "Demean - make less expensive" , "Tried" , "decrease in value" .)