Ernest's mixed gold in dessert wines? (9)
I believe the answer is:
sauternes
'dessert wines?' is the definition.
(I've seen this in another clue)
'ernest's mixed gold in' is the wordplay.
'mixed' is an anagram indicator.
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'in' means one lot of letters goes inside another.
'ernests' with letters rearranged gives 'sternes'.
'sternes' placed around 'au' is 'SAUTERNES'.
(Other definitions for sauternes that I've seen before include "Sweet white wine" , "A sweet Bordeaux" , "Sweet French wine" .)