Abandon what one might do after untying the painter (4,3)

I believe the answer is:

cast off

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

'abandon' is the definition.
(thesaurus)

I cannot understand how the rest of the clue works.

(Other definitions for cast off that I've seen before include "Discard" , "Eliminate stitches - prepare for sea" , "Stop knitting - prepare for sea" , "old garment" , "Finish knitting - go to sea" .)

I've seen this clue in The Hindu.

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.