Catastrophe: ill-temper returns (4)
I believe the answer is:
doom
'catastrophe' is the definition.
(I've seen this before)
'ill-temper returns' is the wordplay.
'ill temper' becomes 'mood'.
'returns' shows that the letters should be reversed in order.
'mood' backwards is 'DOOM'.
(Other definitions for doom that I've seen before include "Fate; ruin" , "Destiny; ruin" , "Condemn to certain destruction" , "Death, destruction" , "Downfall" .)