Commander accepts objective plan of action (6)
I believe the answer is:
agenda
'plan of action' is the definition.
(I've seen this in another clue)
'commander accepts objective' is the wordplay.
'commander' becomes 'aga' (I've seen this before).
'accepts' means one lot of letters goes inside another.
'objective' becomes 'end' (both can mean a purpose).
'aga' placed around 'end' is 'AGENDA'.
(Other definitions for agenda that I've seen before include "Scheme" , "To-do list" , "Topic list for meeting" , "Matters to be addressed" , "List of matters to be discussed at a meeting" .)