Disease also known as hydrophobia (6)
I believe the answer is:
rabies
'disease also known as hydrophobia' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rabies that I've seen before include "Mad dog disease imported from Serbia" , "Disease transmitted through saliva" , "Serbia (anag.)" , "Dangerous viral disease" , "Disease of mad dogs from Serbia" .)