Finally allowing outsiders to depart with everything included (2,3)
I believe the answer is:
in all
'everything included' is the definition.
('in all' can be a synonym of 'everything included')
'finally allowing outsiders to depart' is the wordplay.
'allowing outsiders to depart' indicates the central letters (outside letters are removed).
The centre of 'finally' is 'IN ALL'.
'with' is the link.
(Other definitions for in all that I've seen before include "With everything counted" , "without exception" , "Everything considered" , "after considering everything" , "Completely" .)