Revolutionary animal liberationist keeping account (4)
I believe the answer is:
bill
'account' is the definition.
(billing is a kind of accounting)
'revolutionary animal liberationist keeping' is the wordplay.
'revolutionary' is a reversal indicator.
'keeping' indicates the answer is hidden within the clue.
'llib' can be found hidden inside 'animal liberationist'.
'llib' backwards is 'BILL'.
(Other definitions for bill that I've seen before include "following 28 [SILVER]" , "Statute in draft before it becomes law" , "Police statement" , "Circular - account" , "Promontory; beak" .)