Book of the play (4)
I believe the answer is:
acts
This clue is a double definition.
'book' is the first definition.
(book of the Bible)
'the play' is the second definition.
(I've seen this before)
'of' acts as a link.
(Other definitions for acts that I've seen before include "Behaves or plays" , "Fifth book of the New Testament" , "Book; play parts" , "Does something" , "NT book; laws" .)