Marketeer's minimal stock purchased in Vienna (4)
I believe the answer is:
spiv
'marketeer's' is the definition.
(I have seen 'Black marketeer' mean 'spiv' so perhaps 'marketeer' could also mean 'spiv')
'minimal stock purchased in vienna' is the wordplay.
'minimal' indicates taking the first letters.
The initial letters of 'stock purchased in vienna' is 'SPIV'.
(Other definitions for spiv that I've seen before include "Swindler" , "Agreement" , "Smartly-dressed, but dubious, fellow" , "Sharp operator" , "Old black marketeer" .)