I'm trying to type a single letter into a text box in Photoshop, and then to enlarge the letter so that only part of it is visible in the box. At the moment, when I size the letter beyond the size of the text box it disappears. How can I get it so that I can still see part of the letter inside the box, and so that the rest of it is hidden?
Text frames are not actual objects within a Photoshop file. You can't style them and they don't do anything other than set the area for text to be placed. If the area is smaller than its contained text, the text becomes hidden and little red [+] is shown.
If you want to hide part of a character, you need to do it in other ways, such as a mask on the text layer.