Person shrewd, collecting our rent in oppressive manner (9)

I believe the answer is:

onerously

I'm a little stuck... Click here to teach me more about this clue!

'person shrewd collecting our rent' is the definition.
I can't tell whether this definition defines the answer.

'oppressive manner' is the wordplay.
'oppressive' becomes 'onerous' (I've seen this before).
'manner' becomes 'ly' (I can't explain this - if you can you should believe this answer much more).
'onerous'+'ly'='ONEROUSLY'

'in' acts as a link.

Can you help me to learn more?

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.