Keep the layers warm for infidels! (8)

I believe the answer is:

heathens

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'for infidels' is the definition.
('heathen' can be a synonym of 'infidel')

I can't explain the rest of the clue.

(Other definitions for heathens that I've seen before include "Those who do not believe in the main religions" , "They don't believe in any of the major religions" , "Athens he searched for non-believers" , "pagans" .)

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

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