Thrown out, but Nellie irrepressible (9)
I believe the answer is:
ebullient
'irrepressible' is the definition.
(thesaurus)
'thrown out but nellie' is the wordplay.
'thrown out' indicates an anagram.
'but'+'nellie'='butnellie'
'butnellie' is an anagram of 'EBULLIENT'.
(Other definitions for ebullient that I've seen before include "Bouncing with enthusiasm" , "High-spirited - exhilarated" , "Exuberant, high-spirited" , "Overflowing with enthusiasm" , "Bubbling with enthusiasm" .)