Folder has aged (3)
I believe the answer is:
old
'aged' is the definition.
(similar in meaning)
'folder has' is the wordplay.
'has' indicates a hidden word.
'OLD' can be found hidden inside 'folder'.
(Other definitions for old that I've seen before include "Venerable" , "Obsolete" , "Getting on" , "Wild clematis" , "At an early stage - at a late stage" .)