Crossword Genius

Personal stockpile's made 500 years old (5)

Ross

I believe the answer is:

hoary

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'years old' is the definition.
(thesaurus)

I don't understand the rest of the clue.

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(Other definitions for hoary that I've seen before include "White or grey, or old as of joke" , "Venerably grey" , "Like an old joke" , "Grizzly - ancient" , "Having grey or white hair" .)

I've seen this clue in The Telegraph.
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