A king beset by a depravity - - greed (7)
I believe the answer is:
avarice
'greed' is the definition.
(avarice is a kind of greed)
'a king beset by a depravity' is the wordplay.
'a king' becomes 'ar' (I've seen this in other clues**).
'beset by' indicates putting letters inside ('beset' could historically mean 'cover').
'depravity' becomes 'vice' (I've seen this before).
'a'+'vice'='avice'
'ar' going inside 'avice' is 'AVARICE'.
(Other definitions for avarice that I've seen before include "Excessive greed for wealth" , "A deadly sin" , "Stinginess" , "Eager desire" , "Greed, covetousness" .)