Crossword Genius

What one needs to go beyond Dover say (8)

Ross

I believe the answer is:

passport

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'what one needs' is the definition.
I can't judge whether this defines the answer.

'go beyond dover say' is the wordplay.
'go beyond' becomes 'pass' (synonyms).
'dover say' becomes 'port' (I can't explain this - if you can you should believe this answer much more).
'pass'+'port'='PASSPORT'

'to' is the link.

Can you help me to learn more?

(Other definitions for passport that I've seen before include "that may gain acceptance" , "Document allowing travel abroad" , "you might need Visa with this" , "Carte blanche" , "International identification document" .)

I've seen this clue in The Sun.
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