Rituals upset nieces more (10)

I believe the answer is:

ceremonies

'rituals' is the definition.
(I have seen 'Religious rituals ' mean 'ceremonies' so perhaps 'rituals' could also mean 'ceremonies')

'upset nieces more' is the wordplay.
'upset' is an anagram indicator.
'nieces'+'more'='niecesmore'
'niecesmore' anagrammed gives 'CEREMONIES'.

(Another definition for ceremonies that I've seen is " Religious rituals".)

I've seen this clue in The Guardian.

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