One tail wagging with great joy (7)
I believe the answer is:
'great joy' is the definition.
(I've seen this before)
'one tail wagging' is the wordplay.
'one tail' anagrams to 'ELATION'.
Though, I am not clear how this is indicated.
'with' is the link.
(Other definitions for elation that I've seen before include "Ecstasy -- toenail (anag)" , "Feeling of intense delight" , "Transport" , "'High spirits, exhilaration (7)'" , "Feeling of delight or pride" .)