Sabin developed a vaccine for it (5)
I believe the answer is:
polio
'sabin developed a vaccine for it' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for polio that I've seen before include "Viral disease which can cause paralysis ( 5)" , "Acute viral disease" , "rarely seen complaint" , "Paralysing disease" , "Viral disease causing paralysis" .)