Censorious viewpoint is where reflection begins (8,5)

I believe the answer is:

critical angle

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'where reflection begins' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'censorious viewpoint' is the wordplay.
'censorious' becomes 'critical' (similar in meaning).
'viewpoint' becomes 'angle' (angle is a kind of viewpoint).
'critical'+'angle'='CRITICAL ANGLE'

'is' is the link.

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I've seen this clue in The Daily Express.

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