Determined entrance by one in German domain (7)

I believe the answer is:

doordie

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'determined entrance' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'by one in german domain' is the wordplay.
'by' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'german' becomes 'de' (abbreviation for Deutschland).
'domain' becomes 'door' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'i' going within 'de' is 'die'.
'die' after 'door' is 'DOORDIE'.

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I've seen this clue in The Daily Express.

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