Revolutionary payment method for strike-breaker (4)
I believe the answer is:
scab
'for strike-breaker' is the definition.
(I've seen this in another clue)
'revolutionary payment method' is the wordplay.
'revolutionary' says the letters should be written backwards (letters revolve around).
'payment method' becomes 'BACS' (Bankers' Automated Clearing System).
'bacs' written backwards gives 'SCAB'.
(Other definitions for scab that I've seen before include "Dried surface of wound" , "sign of wound healing" , "one crossing picket line" , "Blackleg - sign of injury" , "Sign of skin wound" .)