This expands when indulging in whiskey and Asti, high on some cocaine (9)
I believe the answer is:
waistline
'this expands when indulging' is the definition.
The definition suggests a singular noun which matches the answer.
'whiskey and asti high on some cocaine' is the wordplay.
'whiskey' becomes 'W' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' says to put letters next to each other.
'high' indicates an anagram (like drunk).
'on some cocaine' becomes 'line' (I can't explain this - if you can you should give a lot more credence to this answer).
'asti' anagrammed gives 'aist'.
'w'+'aist'+'line'='WAISTLINE'
'in' is the link.
Can you help me to learn more?
(Other definitions for waistline that I've seen before include "Swine tail (anag.)" , "measurement" , "It goes round trunk" , "Girth" .)