Tune a Wagnerian may put in a new arrangement (4,2,1,6)

I believe the answer is:

away in a manger

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'tune' is the definition.
(I have seen 'Familiar tune' mean 'away in a manger' so perhaps 'tune' could also mean 'away in a manger')

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for away in a manger that I've seen before include "Familiar tune" , "song?" , "Christmas carol" .)

I've seen this clue in The Times.

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