Penury (9)
There are a few possibilities for this:
pauperism
'penury' is the definition.
(I know that penury can be written as pauperism)
This is all the clue.
(Other definitions for ruin that I've seen before include "dishonour" , "Disaster, collapse" , "State of devastation and destruction" , "financial hardship" , "fall" .)
'penury' is the definition.
(I know that penury can be written as need)
This is the entire clue.
(Other definitions for need that I've seen before include "Penury" , "state requiring relief" , "Desideratum" , "'miss'" , "What's lacking" .)