Turkish leader about to conclude business (6)
I believe the answer is:
agenda
'business' is the definition.
(I've seen this before)
'turkish leader about to conclude' is the wordplay.
'turkish leader' becomes 'aga' (I've seen this before).
'about' is an insertion indicator.
'to conclude' becomes 'end' (I've seen this before).
'aga' going around 'end' is 'AGENDA'.
(Other definitions for agenda that I've seen before include "Items of business for committee meeting" , "Item list for meeting" , "Timetable" , "Meeting's topics" , "Topic list for meeting" .)