Hoary (3)
'hoary' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for olden that I've seen before include "as in time gone by" , "(Of days) in the long distant past!" , "of ancient history?" , "times gone by" , "Of past (times)" .)
'hoary' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for old that I've seen before include "Stale" , "Venerable" , "Advanced in years" , "Former; aged" , "Obsolete" .)