Revolutionary is wrong to back heaven (7)
I believe the answer is:
trotsky
'revolutionary' is the definition.
(I've seen this before)
'wrong to back heaven' is the wordplay.
'wrong' becomes 'tort' (legal term).
'to back' is a reversal indicator.
'heaven' becomes 'sky'.
'tort' written backwards gives 'trot'.
'trot'+'sky'='TROTSKY'
'is' acts as a link.
(Other definitions for trotsky that I've seen before include "Leon --, murdered Russian revolutionary" , "Marxist leader" , "Revolutionary murdered in Mexico" , "Former Communist" , "Russian assassinated in nineteen forty" .)