Amphibian left without its head (3)
I believe the answer is:
eft
'amphibian' is the definition.
(I know that eft is a type of newt)
'left without its head' is the wordplay.
'without its head' means to remove the first letter.
'left' with its first letter taken off is 'EFT'.
(Other definitions for eft that I've seen before include "Kind of newt found in clefts" , "Newt (archaic)" , "Juvenile twenty-three Ac; rhymes with sinister" , "Little creature" , "Young newt" .)