Accepted standard revolutionary rap (3)
I believe the answer is:
par
'accepted standard' is the definition.
(I've seen this before)
'revolutionary rap' is the wordplay.
'revolutionary' says the letters should be written backwards.
'rap' backwards is 'PAR'.
(Other definitions for par that I've seen before include "standard for a pro" , "Black music" , "Face value; equal standing" , "Rap for being average" , "Average - equality" .)