Seaside town — wonderful, fish brought back by trap (5,8)

I believe the answer is:

great yarmouth

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'trap' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

'seaside town wonderful fish brought back by' is the wordplay.
'seaside town' becomes 'yarmouth'.
'wonderful fish' becomes 'taerg' (I can't explain this - if you can you should give a lot more credence to this answer).
'brought back' says the letters should be written backwards.
'by' is a charade indicator (letters next to each other).
'taerg' backwards is 'great'.
'yarmouth' put after 'great' is 'GREAT YARMOUTH'.

Can you help me to learn more?

(Another definition for great yarmouth that I've seen is " Norfolk seaside resort".)

I've seen this clue in The Times.

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