Just click the text to modify and press CTRL+1 to bring the Properties window on the screen. Near the Content label there is the ... content of the text entity. Click inside and delete/insert as you need.
If your text is an mtext entity (multi line text) so click in the content on the Properties window. At the right will appear a button with 3 points. Click it and the Multiline Text Editor will pop up. Operate your changes and click OK.
OK? Did I answer you? Or maybe “cut the text” means that do you wish to place the text in the clipboard for pasting in other applications (a text editor perhaps)?