One serving self is to get sloshed (7)
I believe the answer is:
egotist
'one serving self' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'is to get sloshed' is the wordplay.
'sloshed' indicates an anagram.
'is'+'to'+'get'='istoget'
'istoget' with letters rearranged gives 'EGOTIST'.
Can you help me to learn more?
(Other definitions for egotist that I've seen before include "Conceited and self-centred person" , "Excessively conceited person" , "Self-interested person" , "One absorbed in self" , "show-off" .)