Comprehensive document includes conclusion (8)
I believe the answer is:
detailed
'comprehensive' is the definition.
(I've seen this in another clue)
'document includes conclusion' is the wordplay.
'document' becomes 'deed' (deed is a kind of document).
'includes' is an insertion indicator.
'conclusion' becomes 'tail' ().
'deed' placed around 'tail' is 'DETAILED'.
(Other definitions for detailed that I've seen before include "Elaborate" , "Exhaustive" , "Comprehensive" , "Meticulous" , "Showing attention to fine features" .)