One seeking revolution rejected wrong in courts (4)
I believe the answer is:
trot
'one seeking revolution' is the definition.
(short for Trotskyite)
'rejected wrong in courts' is the wordplay.
'rejected' is a reversal indicator.
'wrong in courts' becomes 'tort' (legal term).
'tort' written backwards gives 'TROT'.
(Other definitions for trot that I've seen before include "moderate movement" , "movement of H [TROT]" , "(Horse's) moderate pace" , "Horse's steady pace" , "Clip (horse)" .)