Coat may be problem for dog (9)
I believe the answer is:
distemper
'coat' is the definition.
(I have seen 'Colourful coat' mean 'distemper' so perhaps 'coat' could also mean 'distemper')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for distemper that I've seen before include "Paint - dog disease" , "Paint; canine disease" , "viral illness" , "Paint; disease of dogs" , "Colourful coat" .)