Regret wasted capital after finance arose (9)
I believe the answer is:
fundament
'regret wasted capital' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'after finance arose' is the wordplay.
'after' is a charade indicator (letters next to each other).
'finance' becomes 'fund' (funding is a kind of financing).
'arose' becomes 'ament' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'fund'+'ament' is 'FUNDAMENT'.
Can you help me to learn more?
(Other definitions for fundament that I've seen before include "bottom" , "Underlying basis - foundation" , "seat" .)