Crossword Genius

Something one might file away secure? (4)

Ross

I believe the answer is:

nail

This clue is a double definition.

'something one might file away' is the first definition.
(as in filing one's nails)

'secure?' is the second definition.
(I've seen this before)

(Other definitions for nail that I've seen before include "Hammered pin" , "Small metal spike" , "Hammer's target" , "Metal spike with head" , "Bring down" .)

I've seen this clue in The Sun and The Times.
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