NT book has an effect (4)
I believe the answer is:
mark
I believe this is a double definition.
'nt book' is the first definition.
(book of the New Testament)
'an effect' is the second definition.
(I know that mark is a type of effect)
'has' acts as a link.
(Other definitions for mark that I've seen before include "Starting point in race" , "Trace" , "Former German monetary unit" , "The second Gospel" , "Gospel writer" .)