Old number from Maigret there (5)

I believe the answer is:

ether

I'm a little stuck... Click here to teach me more about this clue!

'old number' is the definition.
(I've seen this in another clue)

'maigret there' is the wordplay.
'there' anagrams to 'ETHER'.
However, I am not sure how the anagram is indicated.

'from' is the link.

Can you help me to learn more?

(Other definitions for ether that I've seen before include "Anaesthetic; clear sky (poetic)" , "Rare atmosphere" , "number" , "Solvent; clear sky (poet.)" , "Colourless volatile highly inflammable liquid" .)

I've seen this clue in The Sun.

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