Reported vendor offering stock of wine (6)
I believe the answer is:
cellar
'stock of wine' is the definition.
(I've seen this before)
'reported vendor' is the wordplay.
'reported' indicates a 'sounds like' (homophone) clue.
'vendor' becomes 'seller' ('seller' can be a synonym of 'vendor').
'seller' is a homophone of 'CELLAR'.
'offering' is the link.
(Other definitions for cellar that I've seen before include "Bottom room where wine may be stored" , "wine stocks" , "Underground store room" , "Room below ground for storage" , "Underground room - stock of bottled wines" .)