The term IPOD MINI SUCCESSOR is solved by the crossword solution NANO, which is a 4 letter word. The iPod Nano was released in 2005 as the successor to the iPod Mini, and was the first iPod to feature a color display. It was also the first iPod to feature video playback, and it was the first iPod to feature a built-in accelerometer, allowing it to be used as a pedometer. The iPod Nano was discontinued in 2017.