Send off with an expedition (8)
I believe the answer is:
dispatch
This clue is a double definition.
'send off' is the first definition.
('dispatch' can be a synonym of 'send off')
'an expedition' is the second definition.
('dispatch' can be a synonym of 'expedition')
'with' acts as a link.
(Other definitions for dispatch that I've seen before include "Take out" , "Send off (mail)" , "Kill, send off" , "making killing" , "Send (I, not E)" .)