Atmosphere caused by raising catastrophe (4)
I believe the answer is:
mood
'atmosphere' is the definition.
(I've seen this before)
'raising catastrophe' is the wordplay.
'raising' says the letters should be written in reverse.
'catastrophe' becomes 'doom' (I've seen this before).
'doom' backwards is 'MOOD'.
'caused by' acts as a link.
(Other definitions for mood that I've seen before include "State of mind, humour" , "Temporary state of mind" , "An atmosphere of doom" , "melancholy" , "at times appears very high" .)