Reserved arena and sportingly fought (4-6)

I believe the answer is:

ring-fenced

'reserved' is the definition.
(as in ring-fenced funds)

'arena and sportingly fought' is the wordplay.
'arena' becomes 'ring' (I've seen this in other clues).
'and' is a charade indicator (letters next to each other).
'sportingly fought' becomes 'fenced' (fencing is a sport).
'ring'+'fenced'='RING-FENCED'

I've seen this clue in The Guardian.

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