The Torah Kelulah is the Kabbalistic teaching that the Torah has hidden, secret meanings. With all respect to my fellow Jews who are into the Kabbalah, I don't think the Torah has ANY hidden meanings. There are certain things that are harder to understand unless you have the background in Hebrew and the ancient culture of the Israelites. But that is not the Torah being mysterious. It's just you and me not being scholars. An ordinary Jew living say in 600 BCE would not experience these problems.
I don't know how seriously you take the written text of scripture, but I think I speak for anyone who studies it daily and has for decades when I say that how I read a given scripture now is a far cry from how I interpreted it twenty years ago. What I now know, was "hidden" from me when I read it decades ago.
I would go so far as to bet that I could convince you of some meanings in various verses that are hidden from you now, but which I could reveal to you because they've been revealed to me.
To say there's no hidden meaning seems to imply that everyone should read the text and interpret it the same way. There should be complete agreement concerning meaning if nothing is hidden; which, were that the case, would render much of the Talmud a case study in meaninglessness since the sages spend a lot of their time weighing out completely different understandings of the same text, uncovering multifarious hidden possibilities concerning the meaning of a text.
If nothing is hidden, you could read a biblical verse and understand it the same way as a Talmudic scholar who has been trying to uncover deeper meaning from the verse for fifty years.
Have you read the Talmud? Are the interpretations you read the Chachamim giving identical to what you read a verse to mean? Which is a trick question since it's not too frequent that two Talmudic Sages agree with the meaning the other has uncovered through his engagement with the text.
John