Wobbly thing lets in winter air (6,5)

I believe the answer is:

silent night

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'winter air' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'wobbly thing lets in' is the wordplay.
'wobbly' indicates an anagram (I've seen this in other clues).
'thing'+'lets'+'in'='thingletsin'
'thingletsin' anagrammed gives 'SILENT NIGHT'.

Can you help me to learn more?

(Other definitions for silent night that I've seen before include "Christmas carol - hours of undisturbed sleep?" , "Blood sucking mammals" .)

I've seen this clue in The Times.

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