Leaders of Socialist Party instigate new revolution (4)
I believe the answer is:
spin
'revolution' is the definition.
(I know that spin is a type of revolution)
'leaders of socialist party instigate new' is the wordplay.
'leaders of' suggests taking the first letters.
The first letters of 'socialist party instigate new' is 'SPIN'.
(Other definitions for spin that I've seen before include "Mendacious PR; type of bowling" , "Jaunt" , "Rotate like toy top" , "Snip in order to rotate" , "Turn round quickly" .)