Field mouse (4)
I believe the answer is:
vole
'field mouse' is the definition.
(I know that field mouse can be written as vole)
This is all the clue.
(Other definitions for vole that I've seen before include "Small mouse-like rodent" , "Love for a small burrowing mammal" , "Holm-oak" , "Small burrowing animal - love it" , "creature" .)