Mollify bad mood (6)
I believe the answer is:
temper
This clue is a double definition.
'mollify' is the first definition.
(thesaurus)
'bad mood' is the second definition.
(I've seen this before)
(Other definitions for temper that I've seen before include "Make hard by heating and cooling, like iron" , "Mood (often bad)" , "Display of anger" , "Moderate or soften the effects of" , "Angry state of mind" .)