Crossword Genius

I say! Cryptographer's decrypted registry with these books (9)

Ross

I believe the answer is:

apocrypha

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'these books' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

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(Other definitions for apocrypha that I've seen before include "religious text" , "Fourteen books of the Old Testament excluded from most versions of of the Bible" , "Doubtfully-authentic writings" , "dropped books" , "In which Judith is" .)

I've seen this clue in The Telegraph.
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