Cooler chip (4)
I believe the answer is:
nick
This clue is a double definition.
'cooler' is the first definition.
(I've seen this before)
'chip' is the second definition.
(I know that chip can be written as nick)
(Other definitions for nick that I've seen before include "Nab; notch" , "go off with > form" , "Prison - steal" , "A small indentation" , "Thieve" .)