Be hopping mad (4)
'be hopping mad' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for boil that I've seen before include "Painful sore" , "Sore with a hard core filled with pus" , "let off steam" , "Abscess" , "Cook, swelling" .)
(Other definitions for leap that I've seen before include "Jump, spring" , "vault" , "Jump across" , "Spring suddenly" , "Sudden bound" .)