British PM heading off to become citizen of another country (7)

I believe the answer is:

israeli

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

'citizen of another country' is the definition.
'israeli' can be an answer for 'citizen' (I've seen this before). I am not certain of the 'of another country' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for israeli that I've seen before include "Levantine" , "Benjamin Netanyahu, for instance" , "Faithful inhabitant" , "from Mediterranean country" , "Someone from Tel Aviv?" .)

I've seen this clue in The Hindu.

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