Stock of wine merchant picked up (6)
I believe the answer is:
cellar
'stock of wine' is the definition.
(I've seen this before)
'merchant picked up' is the wordplay.
'merchant' becomes 'seller' (seller is a kind of merchant).
'picked up' shows a homophone (sound like).
'seller' sounds like 'CELLAR'.
(Other definitions for cellar that I've seen before include "Container for salt" , "Underground storeroom" , "Wine stock; sounds like vendor" , "Space for storing wine, say" , "Underground room - stock of bottled wines" .)