Steps up to the plate (4)
I believe the answer is:
bats
'steps up to the plate' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for bats that I've seen before include "out to lunch" , "Very eccentric" , "Night-flying creatures" , "Crazy - mammals" , "Take a stab at the night creatures" .)