Fate when state of mind reversed (4)
I believe the answer is:
doom
'fate' is the definition.
('doom' can be a synonym of 'fate')
'state of mind reversed' is the wordplay.
'state of mind' becomes 'mood' (I've seen this before).
'reversed' is a reversal indicator.
'mood' written backwards gives 'DOOM'.
'when' acts as a link.
(Other definitions for doom that I've seen before include "__ and gloom" , "Disastrous fate" , "Terrible fate; death" , "Mood for damnation" , "Judgement" .)