Apart from revolutionary in old hat, turned back (8)
I believe the answer is:
detached
'apart' is the definition.
('detached' can be a synonym of 'apart')
'revolutionary in old hat turned back' is the wordplay.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'in' indicates putting letters inside.
'old hat' becomes 'dated' (I've seen this before).
'turned back' shows that the letters should be reversed in order.
'dated' reversed gives 'detad'.
'che' placed within 'detad' is 'DETACHED'.
'from' acts as a link.
(Other definitions for detached that I've seen before include "Separated from - maybe a house" , "isolated" , "Separate; aloof" , "cut off" , "Unconnected" .)