Animal act, maybe (3)
I believe the answer is:
cat
'animal' is the definition.
(cats are animals)
'act maybe' is the wordplay.
'maybe' indicates an anagram.
'act' anagrammed gives 'CAT'.
(Other definitions for cat that I've seen before include "Animal; converter; boat" , "Domestic animal" , "Common pet" , "See 21" , "Grimalkin" .)