BOGO event (4)
I believe the answer is:
sale
'bogo event' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sale that I've seen before include "Auction; Cheshire town" , "See 12 Down" , "Period of low prices" , "Auction - somewhere in Greater Manchester" , "From which one may get bargains" .)