Very cold car, it unsettled Charlie (6)
I believe the answer is:
arctic
'very cold' is the definition.
(I've seen this before)
'car it unsettled charlie' is the wordplay.
'unsettled' is an anagram indicator.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'car'+'it'='carit'
'carit' anagrammed gives 'arcti'.
'arcti'+'c'='ARCTIC'
(Other definitions for arctic that I've seen before include "icy area" , "Of North polar regions" , "Region around the North Pole" , "Poplar region" , "Area around the North Pole" .)