Essay subject (6)
I believe the answer is:
thesis
'essay subject' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for thesis that I've seen before include "Student dissertation" , "View advanced for purposes of argument" , "Treatise advancing a new point of view resulting from research" , "Research essay written to obtain university degree" , "Analytical essay written for university degree" .)