This once provided light cloak (6)

I believe the answer is:

mantle

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'cloak' is the definition.
(I know that mantle is a type of cloak)

I can't explain the rest of the clue.

(Other definitions for mantle that I've seen before include "Loose outer garment or covering" , "Loose cloak, shawl" , "Lament in loose cloak" , "A cloak, cover" , "Cloak and shelf over the fireplace" .)

I've seen this clue in The Irish News.

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