Unusually cold part of the earth (4)
I believe the answer is:
clod
'the earth' is the definition.
(a clod is a lump of earth)
'unusually cold' is the wordplay.
'unusually' is an anagram indicator.
'cold' is an anagram of 'CLOD'.
'part of' acts as a link.
(Other definitions for clod that I've seen before include "Idiot" , "Compact mass - stupid person" , "Block" , "Lump of earth or clay" , "Lump of turf" .)