To Be Transparent
To Be Clear
intransitive verb, godan verb
Something that is transparent enough for things (like light) to pass through is going to be transparent. In other words, it's going to be clear.
Unlike 透ける, which is more for things that are partially transparent due to being thin or sheer, 透き通る describes things that are totally transparent, clear, or pure — think glass, water, a cloudless sky, or even a clear and pure voice.
The readings for this word are both kun'yomi readings. You've learned both of these readings by now so you should be able to read this on your own.
彼女の手は透き通るほど白かった。
Her hand was so white it was almost transparent.
水が透き通っていてきれい。
The water is very clear and beautiful.
玉ねぎが透き通ってきたら肉を入れてください。
Once the onions become transparent, add the meat.