Bemused with the creature (3)
I believe the answer is:
emu
'the creature' is the definition.
(emu is a kind of creature)
'bemused with' is the wordplay.
'with' indicates a hidden word.
'EMU' can be found hidden inside 'bemused'.
(Other definitions for emu that I've seen before include "Ostrich-like bird" , "Fast runner in Oz" , "Australian bird related to the ostrich" , "Flightless bird of Australia, like ostrich" , "Large Australian flightless bird" .)