I'd colic; ruptured appendix? (7)
I believe the answer is:
codicil
'appendix?' is the definition.
(I know that codicil is a type of appendix)
'i'd colic ruptured' is the wordplay.
'ruptured' indicates anagramming the letters.
'id'+'colic'='idcolic'
'idcolic' is an anagram of 'CODICIL'.
(Other definitions for codicil that I've seen before include "Addendum to will" , "Modifier to will" , "Portion added on to a will" , "Will's rider" , "Additional item appended to a will" .)