Crossword Genius

Goes through three stacks of chalk (7)

Ross

I believe the answer is:

needles

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

'stacks of chalk' is the definition.
(I've seen this before)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for needles that I've seen before include "landmark" , "passes through" , "Rocks off Isle of Wight" , "Is annoying" , "Pins and - -" .)

I've seen this clue in The Telegraph.
Want a hint initially instead of a full solution? Install my app