Special treat - I've gin in salad dressing (11)
I believe the answer is:
vinaigrette
'salad dressing' is the definition.
(vinaigrette is a kind of salad dressing)
'special treat i've gin' is the wordplay.
'special' indicates anagramming the letters.
'treat'+'ive'+'gin'='treativegin'
'treativegin' is an anagram of 'VINAIGRETTE'.
'in' is the link.
(Other definitions for vinaigrette that I've seen before include "sharp dressing" , "French dressing" , "Salad dressing" , "that will be put on the table in France" .)