Turn to revolutionary, in part (8)
I believe the answer is:
rotation
'turn' is the definition.
(rotation is a kind of turn)
'to revolutionary in part' is the wordplay.
'revolutionary' indicates an anagram.
'in' means one lot of letters goes inside another.
'part' becomes 'ration' (ration is a kind of part).
'to' is an anagram of 'ot'.
'ot' inserted inside 'ration' is 'ROTATION'.
(Other definitions for rotation that I've seen before include "Recurrent order" , "Revolutionary movement" , "Out of control" , "Act of turning" , "Recurring sequence" .)