Back-to-back in South Island location (5)

I believe the answer is:

otago

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

'south island location' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'back-to-back' is the wordplay.
'back' says the letters should be written in reverse.
'back' becomes 'ago' ('years back' means 'years ago').
'to' backwards is 'ot'.
'ot'+'ago'='OTAGO'

'in' is the link.

Can you help me to learn more?

(Other definitions for otago that I've seen before include "Old province" , "Antipodean region" , "distant region" , "NZ province" , "New Zealand district" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.