Auction (4)
'auction' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sale that I've seen before include "See 12 Down" , "Auction - somewhere in Greater Manchester" , "Retail event - town in Greater Manchester" , "Exchange of goods for fixed amount" , "From which one may get bargains" .)
(Other definitions for sell that I've seen before include "Retail" , "Betray" , "Trade" , "Dispose of for money" , "Exchange for cash" .)