Freezing cold inside lorry (6)
I believe the answer is:
arctic
'freezing' is the definition.
('arctic' can be a synonym of 'freezing')
'cold inside lorry' is the wordplay.
'cold' becomes 'c' (eg on taps).
'inside' is an insertion indicator.
'lorry' becomes 'artic' (articulated lorry is a semi-trailer truck).
'c' going inside 'artic' is 'ARCTIC'.
(Other definitions for arctic that I've seen before include "Bitter" , "It's cold at the top" , "-- Circle; -- fox" , "icy area" , "Very cold as in the far north" .)