Something lacking from introduction to overseas job (8)
I believe the answer is:
omission
'something lacking' is the definition.
(I've seen this before)
'introduction to overseas job' is the wordplay.
'introduction to' says to take the initial letters.
'job' becomes 'mission' (a mission is a job or task).
The first letter of 'overseas' is 'o'.
'o'+'mission'='OMISSION'
'from' acts as a link.
(Other definitions for omission that I've seen before include "Exclusion" , "Oversight, piece of work neglected" , "Something left out or forgotten" , "Mistake resulting from neglect" , "Something left out or not done" .)