Circular spell of boxing (5)

I believe the answer is:

round

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

This might be a double definition.

'circular' is the first definition.
(synonyms)

'spell of boxing' is the second definition.
'round' can be an answer for 'spell' (thesaurus). I'm not sure about the 'of boxing' bit.

Can you help me to learn more?

(Other definitions for round that I've seen before include "Get applause" , "balls are like this" , "Piece of ammunition" , "Ignore fractions" , "Circular - stage" .)

I've seen this clue in the Sydney Morning Herald.

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