South American or possibly Nigerian ant (11)
I believe the answer is:
'south american' is the definition.
(Argentinian is an example)
'possibly nigerian ant' is the wordplay.
'possibly' indicates an anagram.
'nigerianant' anagrammed gives 'ARGENTINIAN'.
'or' is the link.
(Another definition for argentinian that I've seen is " Eg, native of Buenos Aires".)