Sad case of whiskey leading to vomit (6)
I believe the answer is:
wretch
'sad case' is the definition.
(thesaurus)
'whiskey leading to vomit' is the wordplay.
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'leading to' is a charade indicator (letters next to each other) (some letters go before or lead others).
'vomit' becomes 'retch' (synonyms).
'w'+'retch'='WRETCH'
'of' is the link.
(Other definitions for wretch that I've seen before include "Someone to be pitied" , "Swine" , "Poor devil" , "A poor miserable person" , "Poor unfortunate soul" .)