Disease in grouse (9)
I believe the answer is:
complaint
I believe this clue is a double definition.
'disease' is the first definition.
(I have seen 'A disease' mean 'complaint' so perhaps 'disease' could also mean 'complaint')
'grouse' is the second definition.
(I've seen this before)
'in' acts as a link.
(Other definitions for complaint that I've seen before include "Illness; gripe" , "Negative comment" , "Grievance - may be treated" , "grouse" , "Beef" .)