Assuage anger (6)
I believe the answer is:
temper
This clue is a double definition.
'assuage' is the first definition.
(thesaurus)
'anger' is the second definition.
(temper is a kind of anger)
(Other definitions for temper that I've seen before include "Toughen by gradually heating and cooling" , "Make hard by heating and cooling, like iron" , "Uncontrolled anger" , "Moderate - mood" , "Mood or hardness of metal" .)