Paint; disease of dogs (9)
I believe the answer is:
This clue is a double definition.
'paint' is the first definition.
(I know that distemper is a type of paint)
'disease of dogs' is the second definition.
(I've seen this before)
(Other definitions for distemper that I've seen before include "Paint - disease of animals" , "Kind of paint" , "Water-based paint" , "problem with dogs" , "bad state, being old" .)