Kick off second passenger during meal (6)
I believe the answer is:
launch
'kick off' is the definition.
(I've seen this in another clue)
'second passenger during meal' is the wordplay.
'second passenger' becomes 'a' (2nd letter of 'passenger').
'during' is an insertion indicator.
'meal' becomes 'lunch' (lunch is a kind of meal).
'a' going within 'lunch' is 'LAUNCH'.
(Other definitions for launch that I've seen before include "Set on course, new ship or book" , "Large motorboat" , "Boat; put in the water" , "Establish" , "publicity event" .)