Language used in schooling overseas (5)
I believe the answer is:
lingo
'language' is the definition.
(informal term for language)
'in schooling overseas' is the wordplay.
'in' indicates the answer is hidden within the clue.
'LINGO' is hidden in the letters of 'schooling overseas'.
'used' acts as a link.
(Other definitions for lingo that I've seen before include "Unfamiliar language or jargon" , "local dialect" , "Language (slang)" , "Foreign language or dialect: jargon" , "Vernacular" .)