Next one is ruptured appendix (9)
I believe the answer is:
extension
'appendix' is the definition.
(thesaurus)
'next one is ruptured' is the wordplay.
'ruptured' indicates an anagram.
'next'+'one'+'is'='nextoneis'
'nextoneis' is an anagram of 'EXTENSION'.
(Other definitions for extension that I've seen before include "Annexe" , "telephone number" , "new part of home?" , "Added part" , "new wing" .)