Cooler trouser cut (4)
I believe the answer is:
nick
I believe this clue is a triple definition!
'cooler' is the first definition.
(I've seen this before)
'trouser' is the second definition.
(both can mean steal)
'cut' is the third definition.
(nick is a kind of cut)
(Other definitions for nick that I've seen before include "Steal (slang)" , "Appropriate" , "Little fellow" , "jug" , "go off with > form" .)