Beast in man? I'm a lizard (6)
I believe the answer is:
animal
'beast' is the definition.
(a beast is an animal)
'in man? i'm a lizard' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ANIMAL' can be found hidden inside 'man im a lizard'.
(Other definitions for animal that I've seen before include "Source of meat" , "lamb, perhaps" , "Beast from Manila" , "Uncivilised person" , "' - - Farm', Orwell" .)