Xmas sermoniser met paper-hanger? (9)

I believe the answer is:

decorator

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'xmas' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.

I can't explain the rest of the clue.

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(Other definitions for decorator that I've seen before include "Worker embellishing a property" , "One doing up a house or room" , "Painter perhaps" , "Artisan" , "Painter, wallpaper hanger" .)

I've seen this clue in the Sydney Morning Herald.

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