Unfriendly complaint (4)
I believe the answer is:
cold
I believe this is a double definition.
'unfriendly' is the first definition.
('cold' can be similar in meaning to 'unfriendly')
'complaint' is the second definition.
(cold is a kind of disease)
(Other definitions for cold that I've seen before include "Lacking emotion" , "Frigid" , "Biting" , "Common ailment" , "complaint" .)