Sudden financial gain means ruler overcomes misfortune (7)
I believe the answer is:
killing
'sudden financial gain' is the definition.
'killing' can be an answer for 'gain' (thesaurus). I am not sure about the 'sudden financial' bit.
'ruler overcomes misfortune' is the wordplay.
'ruler' becomes 'king' (king is a kind of ruler).
'overcomes' indicates putting letters inside.
'misfortune' becomes 'ill' (ill is a kind of misfortune).
'king' going around 'ill' is 'KILLING'.
'means' is the link.
Can you help me to learn more?
(Other definitions for killing that I've seen before include "Slaughter" , "Slaying" , "Ending life" , "Execution" , "Deadly; funny" .)