In an annoying way, like a shredder (9)

I believe the answer is:

gratingly

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

'in' is the definition.
Both the definition and answer are adverbs. Maybe there's an association between them I don't understand?

'annoying way like a shredder' is the wordplay.
'annoying' becomes 'grating' (grating is a kind of annoying).
'way' becomes 'L' (abbreviation for left).
'like a shredder' becomes 'y' (I can't justify this - if you can you should give a lot more credence to this answer).
'grating'+'l'+'y'='GRATINGLY'

'an' is the link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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.