Hi-fi (6)
I believe the answer is:
stereo
'hi-fi' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stereo that I've seen before include "Sound transmission through two or more speakers" , "Musical sound with two speakers" , "One might play record" , "Music-playing equipment giving depth of sound" , "Two-channel sound" .)