After a long time, Dan arranged business schedule (6)
I believe the answer is:
agenda
'business schedule' is the definition.
(I've seen this before)
'after a long time dan arranged' is the wordplay.
'after' means one lot of letters go next to another.
'a long time' becomes 'age' ('age' can be a synonym of 'long time').
'arranged' indicates anagramming the letters.
'dan' with letters rearranged gives 'nda'.
'age' put next to 'nda' is 'AGENDA'.
(Other definitions for agenda that I've seen before include "Items of business for committee meeting" , "List of items for discussion by committee" , "Plan for meeting" , "Scheme" , "Topics for a meeting" .)