Reversal of fate, which may be indicative (4)
I believe the answer is:
mood
'indicative' is the definition.
(thesaurus)
'reversal of fate' is the wordplay.
'reversal of' says the letters should be written backwards.
'fate' becomes 'doom' (synonyms).
'doom' backwards is 'MOOD'.
'which may be' is the link.
(Other definitions for mood that I've seen before include "melancholy" , "feelings" , "Feeling of doom" , "Doom (anag)" , "An atmosphere of doom" .)