The tire is toast. If you're stranded the boot techniques others mentioned might get you home. OTOH if you're home now, booting the tire this way can get you stranded.
But I'm surprised nobody mentioned the importance of finding the cause of the cut wall. Not counting a random road object cutting the wall as you ride over it, the number one cause of tire wall damage is abrasion from a slightly high brake shoe. This is especially true if it's a long circular tear. Take a careful look at your brake shoes, and anything else that might be rubbing the tire, so you're not back cin the same place 5 weeks from now.
BTW- a sure tipoff that the brake shoe is too high is a small lip on the top edge of the shoe. This overhangs the rim and cuts tires. You can see and feel it when the wheel is off.
__________________
FB
Chain-L site
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