State of mind could bring back disaster (4)
I believe the answer is:
mood
'state of mind' is the definition.
(one's mood is one's state of mind)
'bring back disaster' is the wordplay.
'bring back' is a reversal indicator.
'disaster' becomes 'doom' (I've seen this in another clue).
'doom' backwards is 'MOOD'.
'could' acts as a link.
(Other definitions for mood that I've seen before include "State of mind or feeling" , "feelings" , "Emotional state" , "Bad feeling" , "Temporary state of mind" .)