Tail one wags in delight (7)

I believe the answer is:

elation

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

'tail one wags' is the wordplay.
'tail one' anagrams to 'ELATION'.
Though, I'm not clear how this is indicated.

'in' is the link.

Can you help me to learn more?

(Other definitions for elation that I've seen before include "'High spirits, exhilaration (7)'" , "Ecstasy -- toenail (anag)" , "Feeling of delight or pride" , "Toenail (anag) -- delight" , "High feeling?" .)

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

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