-How do i make the scan card/tag clear after a period of time with out clearing all the display??
There are two parts to this. First, determining that the unknown period of time has elapsed. To do that, you need to record when the RFID tag was written to the LCD. Then, you need to determine what time it is now. Both of these are done using millis(). The difference between now and then may, or may not exceed some value. If it does, you need to clear part of the screen.
That is done by simply writing a string of spaces to the LCD starting at the same place that you wrote the RFID tag.