Loan shark (6)
I believe the answer is:
usurer
'loan shark' is the definition.
(synonyms)
This is all the clue.
(Other definitions for usurer that I've seen before include "Lender at an exorbitant rate" , "Grasping money-lender" , "One who charges undue interest" , "Person who charges excessive interest on loan" , "Extortionist" .)