The vending of ales? (4)
I believe the answer is:
sale
'the vending' is the definition.
(thesaurus)
'of ales?' is the wordplay.
'of' indicates an anagram (the answer comes from or 'of' the letters).
'ales' with letters rearranged gives 'SALE'.
(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" .)