Prehistoric egg laid emptily (3)

I believe the answer is:

old

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'prehistoric' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for old that I've seen before include "Advanced in years" , "Obsolete" , "Getting on" , "Ancient" , "Elderly" .)

I've seen this clue in the Sydney Morning Herald.

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