Divinity is the subject of study (8)
I believe the answer is:
theology
'divinity' is the definition.
('theology' can be a synonym of 'divinity')
'the subject of study' is the wordplay.
'subject of study' becomes 'ology' (I've seen this before).
'the'+'ology'='THEOLOGY'
'is' acts as a link.
(Other definitions for theology that I've seen before include "Bible study" , "Study of religious beliefs" , "Religious studies" , "Study of God, etc" , "Study of religious questions" .)