Mood affected destiny (4)
I believe the answer is:
'destiny' is the definition.
(I know that doom is a type of destiny)
'mood affected' is the wordplay.
'affected' indicates an anagram.
'mood' is an anagram of 'DOOM'.
(Other definitions for doom that I've seen before include "Condemn (to certain death?)" , "Terrible fate; death" , "Mood for damnation" , "Bad destiny" , "Fate; ruin" .)