Cool wine locked away (2,4)
I believe the answer is:
in hock
'locked away' is the definition.
(in hock can mean in prison)
'cool wine' is the wordplay.
'cool' becomes 'in' ('in' can mean fashionable or cool).
'wine' becomes 'hock' (hock is a kind of wine).
'in'+'hock'='IN HOCK'
(Other definitions for in hock that I've seen before include "Put away" , "behind bars" , "Pledged" , "owing money" , "being kept by uncle" .)