Druidess occasionally left mixture of gin and wine (8)
I believe the answer is:
riesling
'wine' is the definition.
(Riesling is an example)
'druidess occasionally left mixture of gin' is the wordplay.
'occasionally' means one should take alternating letters.
'left' becomes 'l' (common abbreviation).
'mixture of' is an anagram indicator (I've seen this in other clues).
The alternate letters of 'druidess' are 'ries'.
'gin' with letters rearranged gives 'ing'.
'ries'+'l'+'ing'='RIESLING'
'and' is the link.
(Other definitions for riesling that I've seen before include "Aromatic white wine from the Rhine valley" , "Strange wine for Sir Ingle" , "Gin riles the wine" , "Dry white wine (German)" , "Fragrant white wine from the Rhine valley or from California" .)