Aged folder contains it (3)

I believe the answer is:

old

I'm a little stuck... Click here to teach me more about this clue!

'it' is the definition.
The definition suggests a singular noun which matches the answer.

'aged folder contains' is the wordplay.
'contains' indicates a hidden word.
'OLD' is hidden in the letters of 'aged folder'.

Can you help me to learn more?

(Other definitions for old that I've seen before include "Getting on" , "Obsolete" , "Stale" , "Former; aged" , "Long-lived" .)

I've seen this clue in The Mirror.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.