Rich person (3,3)
I believe the answer is:
fat cat
'rich person' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for fat cat that I've seen before include "Wealthy person like obese beline" , "Someone (undeservedly?) rich in business" , "Influential politician" , "Wealthy and powerful person (informal)" , "Magnate" .)