South African swimmer in Massachusetts (4,3)
I believe the answer is:
cape cod
'massachusetts' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I don't see?
'south african swimmer' is the wordplay.
'south african' becomes 'cape' (I can't justify this - if you can you should believe this answer much more).
'swimmer' becomes 'cod' (type of fish).
'cape'+'cod'='CAPE COD'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for cape cod that I've seen before include "part of Massachusetts" , "part of New England?" , "American resort" , "US peninsula" , "Popular holiday destination for Bostonians" .)