Downfall, collapse (4)
I believe the answer is:
ruin
I believe this clue is a double definition.
'downfall' is the first definition.
(I know that downfall can be written as ruin)
'collapse' is the second definition.
(I've seen this before)
(Other definitions for ruin that I've seen before include "Catastrophe" , "loss of position" , "financial hardship" , "Reduce to bankruptcy" , "Physical collapse" .)