Half of police are finishing early, freezing cold (5)
I believe the answer is:
polar
'freezing cold' is the definition.
(as in the North and South Poles)
'half of police are finishing early' is the wordplay.
'half of' suggests halving the letters.
'finishing early' means to remove the last letter (the word finishes earlier than normal).
'police' with half the letters taken is 'pol'.
'are' with its last letter removed is 'ar'.
'pol'+'ar'='POLAR'
(Other definitions for polar that I've seen before include "Of the far north or south" , "White bear" , "Kind of bear or opposite" , "Relating to icy regions" , "-- Bear; -- circle" .)