Mouldy (5)
'mouldy' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for stale that I've seen before include "No longer fresh" , "Not fresh, being least" , "no longer bearing interest?" , "Unfresh" , "Boring" .)
'mouldy' is the definition.
(I know that mouldy can be written as musty)
This is all the clue.
(Other definitions for musty that I've seen before include "Stale, mouldy-smelling" , "Mouldy; stale-smelling" , "Smelling stale or damp" , "Stale and dank" , "Mouldy; outdated" .)