Reveal fourth dimension at start of performance (8)

I believe the answer is:

showtime

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

'reveal fourth dimension' is the wordplay.
'reveal' becomes 'show' (synonyms).
'fourth dimension' becomes 'time' (time is sometimes considered the fourth dimension).
'show'+'time'='SHOWTIME'

'at' acts as a link.

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I've seen this clue in The Daily Express.

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