Unopened wine is acceptable (4)
I believe the answer is:
okay
'acceptable' is the definition.
(I've seen this in another clue)
'unopened wine' is the wordplay.
'unopened' means to remove the first letter (without opening letter).
'wine' becomes 'Tokay' (Tokay is an example).
'tokay' with its initial letter removed is 'OKAY'.
'is' is the link.
(Other definitions for okay that I've seen before include "Common jargon for yes, all right" , "Agree" , "All right; sanction" , "Correct" , "Agreed!" .)