Article written in ancient Hebrew (3)
I believe the answer is:
the
'article' is the definition.
(the definite article in English)
'written in ancient hebrew' is the wordplay.
'written in' indicates the answer is hidden within the clue.
'THE' is hidden within 'ancient hebrew'.
(Other definitions for the that I've seen before include "Article is quite definite" , "SECOND PART OF 23" , "and 24 Down: Similar things" , "Last words of story" , "See 10 Across" .)