Cook in hot water (4)
I believe the answer is:
boil
'cook in hot water' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for boil that I've seen before include "Painful sore" , "Cook in hot water" , "Bubble up - inflamed swelling" , "Cook, swelling" , "Eruption of the skin" .)