Bad article, to a degree, united party spontaneously (10)

I believe the answer is:

offthecuff

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'spontaneously' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'bad article to a degree united' is the wordplay.
'bad' becomes 'off' (eg meat that's gone off is bad).
'article' becomes 'the' (the definite article in English).
'to a degree' becomes 'cuff' (I can't explain this - if you can you should believe this answer much more).
'united' means one lot of letters go next to another.
'off'+'the'+'cuff'='OFFTHECUFF'

'party' is the link.

Can you help me to learn more?

I've seen this clue in The Irish Times.

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