An ultra sloshed is wild (7)
I believe the answer is:
natural
'is wild' is the definition.
(synonyms)
'an ultra sloshed' is the wordplay.
'sloshed' indicates anagramming the letters.
'an'+'ultra'='anultra'
'anultra' is an anagram of 'NATURAL'.
(Other definitions for natural that I've seen before include "in a pack, not wild?" , "Frank < , twenty-one" , "Accidental" , "Not artificial; off-white" , "white key on a piano?" .)