The term 'STEREO PART' can be broken down into two crossword solutions: AMP (3 letters) and LOUDSPEAKER (11 letters). An amplifier, or amp, is an electronic device that increases the strength of a signal. It is commonly used in audio systems to increase the volume of sound. A LOUDSPEAKER is an electroacoustic transducer that converts electrical signals into sound waves. It is the main component of a sound system, and is responsible for producing sound from audio signals.