Cocktail of starch is a means of purification (9)
I believe the answer is:
catharsis
'of purification' is the definition.
'catharsis' can be an answer for 'purification' (I've seen this before). I'm not sure about the 'of' bit.
'cocktail of starch is a' is the wordplay.
'cocktail of' indicates anagramming the letters (a mixture of the letters).
'starch'+'is'+'a'='starchisa'
'starchisa' is an anagram of 'CATHARSIS'.
'means' is the link.
Can you help me to learn more?
(Other definitions for catharsis that I've seen before include "purging process" , "Purification - is rash act (anag)" , "cleansing'" , "Emotional release" , "Process of releasing pent-up emotions" .)