What may need filing is secure (4)

I believe the answer is:

nail

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'is secure' is the definition.
(both can mean to apprehend or capture)

I don't understand the remainder of the clue.

(Other definitions for nail that I've seen before include "Horny substance on finger or toe" , "Finger end; fasten" , "Amall metal spike" , "one wouldn't want in one's coffin?" , "Digital plate" .)

I've seen this clue in The Irish Times.

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