Clue: Howl – wound's beginning to ulcerate badly (9)
Answer: CATERWAUL
Explanation: Definition: Howl
*(ulcerate w) (although see comments 3 and 4 below – I was too annoyed at the W that I didn't notice that CATERWAUL needs two As, and not two Es!) 
Not entirely comfortable with the W being part of the anagram when "to" splits it from the rest of the anagram fodder. This would normally imply that the W should be added to the anagram at the beginning or end, rather than in the middle.