Hi @vshukla22,
A warm welcome to the Bunnings Workshop community, it is fantastic to have you with us.
This is called skeletonisation, and it is where an insect eats the soft parts of the leaf but leaves the leaf veins behind.
We'll have to know what insect is causing it to offer the best advice possible.
If you inspect the plants, can you see any insects?
They could be feeding at night, so inspecting them after dark would be worthwhile to help identify the culprits.
Without identifying the culprits, you could try spraying your basil with Pyrethrum, which is effective at controlling a variety of insects that could be the culprit. It is fine for use on edible plants, but I would give the leaves a good clean before consumption.
Allow me to tag @Noelle and @mich1972 to see if they have any thoughts.
Let me know what you think and if you have further questions, please don't hesitate to reach out.
Jacob
