Crossword Genius

Island all right to an extent that Yankee leaves (7)

Ross

I believe the answer is:

okinawa

I'm a little stuck... Click here to teach me more about this clue!

'island' is the definition.
(I know that Okinawa is a island)

'all right to an extent that yankee leaves' is the wordplay.
I cannot quite see how this works, but
'right' could be 'ok' (both are affirmative answers) and 'ok' is found within the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
This explanation may well be incorrect...

Can you help me to learn more?

(Other definitions for okinawa that I've seen before include "coral island" , "Japanese location" , "Japanese city" , "American victory, June 1945" , "Japanese island, capital Naha" .)

I've seen this clue in The Sun.
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