What are said to be places for wine merchants (7)
I believe the answer is:
sellers
'merchants' is the definition.
(seller is a kind of merchant)
'what are said to be places for wine' is the wordplay.
'what are said to be' indicates a 'sounds like' (homophone) clue.
'places for wine' becomes 'cellars'.
'cellars' is a homophone of 'SELLERS'.
(Other definitions for sellers that I've seen before include "kind of market" , "Peter" , "British actor, star of the 17" , "Vendors" .)