Girl's mood that may affect dog (9)
I believe the answer is:
distemper
'dog' is the definition.
(thesaurus)
'girl's mood' is the wordplay.
'girl' becomes 'dis' (I've seen this in other clues).
'mood' becomes 'temper' (temper is one's mood or state of mind).
'dis'+'temper'='DISTEMPER'
'that may affect' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for distemper that I've seen before include "problem with dogs" , "Kind of paint" , "Viral disease" , "that's bad for kennels" , "problem for pet" .)