Not sure what you mean by "clickable". If you mean can you select, and then copy text in pages...then yes, it's built-in. Just press and hold on the text, then a pair of bookends will appear and the word between will be highlighted. You can move the bookends to capture more or less text. Alternatively you can click on the box at the top that has 4 squares in it (or the words SELECT ALL - depending on your version/phone), and it will select ALL text. Once you've selected what you want, you can click on the other boxes above to cut (scissors) or copy (two papers stacked). You can also email, share in text, etc.
If you mean somehow making plain text in a webpage into a hyperlink to take you to a search, for instance, you can use the method above and Paste it into the address bar of the browser, or into a Google search window.
If that's not what you're looking for, then I'm lost.