Nocturnal creature (3)
(Other definitions for bat that I've seen before include "Small mammal or cricket striker" , "Small flying mammal - like 11 Across" , "Wooden implement for cricket" , "Creature" , "A mammal; a club" .)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">nocturnal creature</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for owl that I've seen before include "Bird of the 18" , "Traditionally wise bird" , "Head-swivelling night bird" , "Bird of prey with front-facing eyes" , "Harry Potter's Hedwig, for instance" .)
(Another definition for fieldmouse that I've seen is " rodent".)