Moderate mood (6)
I believe the answer is:
temper
This clue is a double definition.
'moderate' is the first definition.
(I know that moderate can be written as temper)
'mood' is the second definition.
(temper is one's mood or state of mind)
(Other definitions for temper that I've seen before include "Irritability" , "Frame of mind" , "Angry state of mind" , "Toughen by gradually heating and cooling" , "Make harder" .)