Woman's mood is a disease (9)
I believe the answer is:
distemper
'disease' is the definition.
(distemper is a kind of health problem)
'woman's mood' is the wordplay.
'woman's' becomes 'dis' (Di is short for Diana).
'mood' becomes 'temper' (temper is one's mood or state of mind).
'dis'+'temper'='DISTEMPER'
'is a' acts as a link.
(Other definitions for distemper that I've seen before include "that's bad for kennels" , "Paint; disease of dogs" , "viral illness" , "Paint; canine disease" , "Viral infection < found in lab" .)