Endlessly regretting penury (4)
I believe the answer is:
ruin
'penury' is the definition.
The answer and definition can be both states of affairs as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'endlessly regretting' is the wordplay.
'endlessly' means to remove the last letter.
'regretting' becomes 'ruing' ('rue' can be a synonym of 'regret').
'ruing' with its last letter taken off is 'RUIN'.
Can you help me to learn more?
(Other definitions for ruin that I've seen before include "Disaster, collapse" , "financial disaster" , "State of devastation and destruction" , "Dilapidated building" , "Destroy; downfall" .)