Fate brings a bad mood (4)
I believe the answer is:
doom
'fate' is the definition.
(I know that fate can be written as doom)
'a bad mood' is the wordplay.
'a bad' indicates an anagram.
'mood' with letters rearranged gives 'DOOM'.
'brings' is the link.
(Other definitions for doom that I've seen before include "Downfall" , "Inevitable ruin" , "Disastrous fate" , "Condemn to certain destruction" , "__ and gloom" .)