Back in the day (4)
'back in the day' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for once that I've seen before include "in bygone days" , "Previously" , "in days of yore?" , "in bygone era" , "Cone (anag.)" .)
'back in the day' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Another definition for years ago that I've seen is " Way back".)