Clue: Island that's taken over island that's taken over island (6)
Answer: TAHITI
Explanation: Definition: island
I think I have the right definition! A reversal (the second 'that's taken over') of I (the first 'island') plus TIHAT, an envelope (the first 'taken over') of I (the second 'island') in 'that' (the first). And the party of the first part ….