The vending of ales? (4)
I believe the answer is:
sale
'the vending' is the definition.
(thesaurus)
'ales?' is the wordplay.
'ales' anagrams to 'SALE'.
But, I'm not clear how the anagram is indicated.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for sale that I've seen before include "Exchange of goods for fixed amount" , "From which one may get bargains" , "Occasion for buying at reduced prices" , "Clearance of goods at reduced prices" , "Retail event - town in Greater Manchester" .)