Disease or illness (6)
I believe the answer is:
malady
I believe this is a double definition.
'disease' is the first definition.
(malady is a kind of health problem)
'illness' is the second definition.
(malady is a kind of health problem)
'or' is the link.
(Other definitions for malady that I've seen before include "Sickness, ailment" , "Sickness or disease" , "Disease or disorder" , "Complaint" , "hay fever, perhaps" .)