Diary emptied to accommodate private sector function (6,5)
I believe the answer is:
'function' is the definition.
(I have seen 'social function' mean 'dinner party' so perhaps 'function' could also mean 'dinner party')
'diary emptied to accommodate private sector' is the wordplay.
'emptied' means to remove the middle letters.
'to accommodate' indicates putting letters inside.
'private' becomes 'inner' (as in one's private or inner thoughts).
'sector' becomes 'part' (both can mean a segment).
'diary' with its middle taken out is 'dy'.
'dy' enclosing 'innerpart' is 'DINNER PARTY'.
(Other definitions for dinner party that I've seen before include "Social gathering over a meal" , "social function" , "Sociable gathering for meal" .)