Sore; fistula (5)
I believe the answer is:
ulcer
I believe this is a double definition.
'sore' is the first definition.
(I've seen this in another clue)
'fistula' is the second definition.
(thesaurus)
(Other definitions for ulcer that I've seen before include "Cruel kind of body sore" , "Cruel sort of body sore" , "Cruel sort of open sore" , "Sore spot" , "Inflammatory internal or external lesion" .)