Doom fixed by temper (4)
I believe the answer is:
mood
'temper' is the definition.
(I know that temper can be written as mood)
'doom fixed' is the wordplay.
'fixed' indicates an anagram.
'doom' anagrammed gives 'MOOD'.
'by' is the link.
(Other definitions for mood that I've seen before include "State of mind, humour" , "State of mind or emotion" , "Emotional state" , "State of mind or feeling" , "feelings" .)