The low fellow has evidence of debts - bearing much interest! (7)
I believe the answer is:
curious
'the low fellow' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'evidence of debts bearing much interest' is the wordplay.
'evidence of debts' becomes 'IOUs' (I Owe Yous, promises to pay debts).
'bearing' means one lot of letters go next to another.
'much interest' becomes 'cur' (I can't justify this - if you can you should give a lot more credence to this answer).
'ious' put after 'cur' is 'CURIOUS'.
'has' is the link.
Can you help me to learn more?
(Other definitions for curious that I've seen before include "Odd - inquisitive" , "Eager to know; strange" , "Strange - inquisitive" , "Keen to learn" , "Strange, unusual" .)