An oil lamp goes out (4)

I believe the answer is:

palm

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

'lamp goes out' is the wordplay.
'goes out' is an anagram indicator.
'lamp' with letters rearranged gives 'PALM'.

Can you help me to learn more?

(Other definitions for palm that I've seen before include "Conceal magician" , "Obscure" , "Leaf in part of the hand?" , "Coconut-bearing tree" , "Tropical tree; conceal" .)

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

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