Others, into Old English, ripping up Greek plays (8)
I believe the answer is:
oresteia
'greek plays' is the definition.
(I've seen this before)
'others into old english ripping up' is the wordplay.
'others' becomes 'rest' (I've seen this before).
'into' means one lot of letters goes inside another.
'old english' becomes 'oe'.
'ripping' becomes 'ai' (A1, term for 'excellent').
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'ai' reversed gives 'ia'.
'rest' put within 'oe' is 'oreste'.
'oreste'+'ia'='ORESTEIA'
(Other definitions for oresteia that I've seen before include "Play trilogy by Aeschylus, see a riot (anag.)" , "Greek plays" , "Aeschylus's play trilogy" , "three tragedies for Aeschylus" .)