Angles ceased to be right: too short (8)

I believe the answer is:

diedrals

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

'ceased to be right too short' is the wordplay.
'ceased' becomes 'died'.
'to be right' becomes 'R' (common abbreviation).
'too' becomes 'also' (synonyms).
'short' means to remove the last letter.
'also' with its last letter taken off is 'als'.
'died'+'r'+'als'='DIEDRALS'

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I've seen this clue in The Times.

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