Theatrical end arguably has hidden agenda (8)
I believe the answer is:
calendar
'agenda' is the definition.
(thesaurus)
'theatrical end arguably has hidden' is the wordplay.
'hidden' indicates the answer is hidden within the clue.
'CALENDAR' is hidden within 'theatrical end arguably has'.
(Other definitions for calendar that I've seen before include "that's dated" , "Diary" , "Schedule" , "Tabular array of days" , "System for dividing the year" .)