Plays, regularly polemical, without intermission (8)
I believe the answer is:
oresteia
'plays' is the definition.
(I know that Oresteia Theatricalia play ID 4dy)
'regularly polemical without intermission' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'without' is an insertion indicator ('without' can be similar in meaning to 'outside').
'intermission' becomes 'rest' (rest is a kind of intermission).
The alternate letters of 'polemical' are 'oeia'.
'oeia' going around 'rest' is 'ORESTEIA'.
(Other definitions for oresteia that I've seen before include "Aeschylus's play trilogy" , "Greek plays" , "Play trilogy by Aeschylus, see a riot (anag.)" , "three tragedies for Aeschylus" .)