No longer fresh
'no longer fresh' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stale that I've seen before include "Mouldy or hackneyed" , "Least (anag.)" , "Unfresh" , "no longer bearing interest?" , "Boring" .)
(Other definitions for old that I've seen before include "Venerable" , "At an early stage - at a late stage" , "Senescent" , "Much-used" , "Wild clematis" .)