Arresting boxing scrap, very exciting (4-6)

I believe the answer is:

nail-biting

'very exciting' is the definition.
(nail-biting can mean exciting or tense)

'arresting boxing scrap' is the wordplay.
'arresting' becomes 'nailing' ('nail' can be a synonym of 'arrest').
'boxing' means one lot of letters goes inside another ('box' can mean contain, as in to put in a box).
'scrap' becomes 'bit' (synonyms).
'nailing' enclosing 'bit' is 'NAIL-BITING'.

I've seen this clue in The Guardian.

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