Short description, covering illness (6)
I believe the answer is:
typhus
'illness' is the definition.
(typhus is a kind of illness)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for typhus that I've seen before include "Disease found in spy hut, strangely" , "Infectious disease with fever and purple rash" , "Dangerous fever transmitted by lice" , "Disease causing high fever and skin rash" , "Acute, infectious fever" .)