Repelled a raven, largely predatory beast (4)
I believe the answer is:
orca
'beast' is the definition.
(I know that orca is a type of dolphin)
'repelled a raven largely predatory' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
The remaining letters 'orc' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for orca that I've seen before include "Marine creature" , "School killer" , "Large predator" , "Predatory black and white toothed whale" , "Killer at sea" .)