Two flats? That sounds rich (6)
I believe the answer is:
loaded
'rich' is the definition.
(similar in meaning)
I can't explain the remainder of the clue.
(Other definitions for loaded that I've seen before include "Burdened; rich (slang)" , "Big Bertha sometimes was" , "Wealthy (slang) - drunk (slang)" , "Charged with ammunition" , "Biased, wealthy (colloq.)" .)