Hide argument but knit one's brow? (6)

I believe the answer is:

furrow

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

'knit one's brow?' is the definition.
'furrow' can be an answer for 'knit' (thesaurus). I'm not sure about the 'one's brow?' bit.

'hide argument' is the wordplay.
'hide' becomes 'fur' (I've seen this before).
'argument' becomes 'row' (to row is to argue).
'fur'+'row'='FURROW'

'but' acts as a link.

Can you help me to learn more?

(Other definitions for furrow that I've seen before include "Shallow trench made by a plough" , "Channel; wrinkle" , "'Rut, groove (6)'" , "Ploughing mark" , "Ploughed trench" .)

I've seen this clue in the Sydney Morning Herald.

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.