Animal less cold in the East End (5)
I believe the answer is:
otter
'animal' is the definition.
(I know that otter is a type of animal)
'less cold in the east end' is the wordplay.
'less cold' becomes 'hotter' ('hot' can be the opposite of 'cold' so perhaps 'hotter' is reasonable for 'less cold').
'in the east end' means to remove the first letter (drop a letter, as a cockney might).
'hotter' with its initial letter taken away is 'OTTER'.
(Other definitions for otter that I've seen before include "carnivore is concerned" , "Sleek river mammal" , "Semi-aquatic creature" , "furry creature" , "furry animal" .)