How do I stop ants from crawling on my outside clothes line?

https://www.rd.com/home/cleaning-organizing/13-common-items-for-getting-rid-of-ants/

Clean the line with vinegar. It will obscure the trail and clean your line. You can also use a citric scented cleaner. They don’t like that either.

Put some Jiffy Corn Muffin mix near the site where they climb up. They’ll take it back to the nest and die.

Put some Vaseline on the poles. They can't climb through it.

Vaseline where they crawl up

There is no one time permanent solution. Treat the ground around the supports with a commercially available pesticide labeled for ants ona consistant scheduke during the warm months of the year. (retired pest control operator)

I have a resealable container with a mix of vinegar and lemon juice kept inside. Every time we are about to go use the line we take the sponge out of the container and wipe down the line with it.

As joh32721025 said, there is no permanent solution to the problem, new ants come out every year. I use vinegar on the lines and poles, temporary, but it works.

How about a bait trap? https://www.hometalk.com/diy/outdoor/pest-repeller/quick-dyi-sweet-bait-to-treat-and-get-rid-of-your-ants-18515410