Kept up by bonehead, negative plan (6)
I believe the answer is:
agenda
'plan' is the definition.
(agenda is a kind of plan)
'kept up by bonehead negative' is the wordplay.
'AGENDA' is hidden back-to-front within the letters.
However, I'm uncertain how this is indicated.
Can you help me to learn more?
(Other definitions for agenda that I've seen before include "List of things to be done or discussed" , "plan of things to be done" , "Items of business for committee meeting" , "Business to be transacted" , "To-do list" .)