Succeeded in real estate, securing one affluence (10)
I believe the answer is:
Here is my best explanation:
'affluence' is the definition.
'succeeded in real estate securing one' is the subsidiary indication.
'succeeded' becomes 's' (genealogical abbreviation).
'in' means one lot of letters goes inside another.
'real estate' becomes 'property' (I've seen this before**).
'securing' means one lot of letters goes inside another.
'one' becomes 'i' (roman numeral).
's' put within 'property' is 'prosperty'.
'prosperty' going around 'i' is 'prosperity'.
(Other definitions for prosperity that I've seen before include "Financial success", "Things going well", "wealth" and "Wealth".)