Crossword Genius

Place for a ring in Superman’s change room (5,5)

Ross

I believe the answer is:

phone booth

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

'room' is the definition.
(phone booth is a kind of room)

'place for a ring in superman's change' is the wordplay.
I cannot really understand how this works, but
'a' could be 'one' and 'one' is found within the answer.
'ring' could be 'o' (letter resembling a ring) and 'o' is found in the answer.
This explanation may well be incorrect...

Can you help me to learn more?

I've seen this clue in The Hindu.
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