Richness, affluence (6)
I believe the answer is:
wealth
I believe this is a double definition.
'richness' is the first definition.
(I know that richness can be written as wealth)
'affluence' is the second definition.
(I've seen this in another clue)
(Other definitions for wealth that I've seen before include "Material worth" , "Riches, worldly goods" , "Abundance of resources" , "Mammon" , "was common under Cromwell" .)