Hound in fatal outbreak (6)
I believe the answer is:
plague
I believe this clue is a double definition.
'hound' is the first definition.
(I've seen this in another clue)
'fatal outbreak' is the second definition.
(I've seen this before)
'in' is the link.
(Other definitions for plague that I've seen before include "Pestilential epidemic" , "Contagious disease that spreads rapidly and kills many" , "Deadly contagious disease, or a swarm of locusts" , "Widespread, contagious and destructive disease" , "Contagious disease with a high death rate" .)