Eat ravenously when course is over (4)
I believe the answer is:
wolf
'eat ravenously' is the definition.
'course is over' is the wordplay.
'course' becomes 'flow' (flow is a kind of course).
'is over' is a reversal indicator.
'flow' backwards is 'WOLF'.
'when' acts as a link.
(Other definitions for wolf that I've seen before include "Carnivorous mammal" , "See 2" , "Lupine animal" , "SECOND PART OF 14" , "Beast, member of pack" .)