Cold-blooded creature clever duke abandoned (3)
I believe the answer is:
eft
'cold-blooded creature' is the definition.
(term for a young newt)
'clever duke abandoned' is the wordplay.
'clever' becomes 'deft' (deft means skilful or clever).
'duke' becomes 'd' (abbreviation).
'abandoned' is a deletion indicator.
'deft' with 'd' removed is 'EFT'.
(Other definitions for eft that I've seen before include "Pond creature" , "Juvenile twenty-three Ac; rhymes with sinister" , "Slimy creature" , "Swimmer with feeble legs" , "Small amphibian" .)