Mice, to owls (4)
I believe the answer is:
prey
'mice to owls' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for prey that I've seen before include "Animal hunted by another for food" , "Animal's quarry" , "Animal sought as food" , "Quarry, target" , "Hunted creature" .)