Case of wine, fine mixture (9)
I believe the answer is:
portfolio
'case' is the definition.
(I know that portfolio is a type of case)
'wine fine mixture' is the wordplay.
'wine' becomes 'port' (port wine is a kind of wine).
'fine mixture' becomes 'folio' (I've seen this in other clues).
'port'+'folio'='PORTFOLIO'
'of' acts as a link.
(Other definitions for portfolio that I've seen before include "Large case" , "Flat case for paper sheets" , "Case for loose paper, drawings etc" , "Set of investments held by one person" , "Shares" .)