Ant bite upsets the foreigner (7)
I believe the answer is:
tibetan
'foreigner' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'ant bite upsets' is the wordplay.
'upsets' indicates an anagram.
'ant'+'bite'='antbite'
'antbite' anagrammed gives 'TIBETAN'.
'the' is the link.
Can you help me to learn more?
(Other definitions for tibetan that I've seen before include "Nationality of citizen of Lhasa, before Chinese invasion" , "mountain man, say" , "Himalayan language" , "from high land" , "From Lhasa, perhaps" .)