Sudden windfall (7)
I believe the answer is:
bonanza
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">sudden windfall</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for bonanza that I've seen before include "Mine of wealth" , "Source of great and sudden wealth" , "Source of wealth or good fortune" , "Huge stroke of luck" , "Sudden and unexpected source of wealth" .)