Excessive interest (5)
I believe the answer is:
usury
'excessive interest' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for usury that I've seen before include "Taking excessive interest" , "Taking a lot of interest" , "Shylock's calling" , "Lending money at excessive rates of interest" , "The lending of money at high rates" .)