U.S. peninsula or South African fish (4,3)

I believe the answer is:

cape cod

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'u s peninsula' is the definition.
The definition suggests a singular noun which matches the answer.

'south african fish' is the wordplay.
'south african' becomes 'cape' (I can't explain this - if you can you should believe this answer much more).
'fish' becomes 'cod' (type of fish).
'cape'+'cod'='CAPE COD'

'or' is the link.

Can you help me to learn more?

(Other definitions for cape cod that I've seen before include "Peninsula in Massachusetts" , "American resort" , "New England promontory" , "part of New England?" , "East coast resort" .)

I've seen this clue in the Evening Standard.

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