No longer available (4)
'no longer available' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gone that I've seen before include "Departed, disappeared" , "Departed; used up" , "Away, departed" , "Moved - died" , "... saga of 2's civil war" .)
(Other definitions for down the drain that I've seen before include "Wasted" , "Where water board worker might be" .)