As in pre-stage makeup (12)

I believe the answer is:

greasepaints

I'm a little stuck... Click here to teach me more about this clue!

'makeup' is the definition.
(I know this)

'as in pre-stage' is the wordplay.
'as in pre-stage' can be anagrammed to 'GREASEPAINTS'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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