Music player debuts in Sydney this evening, rocking expensive oboe (6)
I believe the answer is:
stereo
'music player' is the definition.
(I've seen this in another clue)
'debuts in sydney this evening rocking expensive oboe' is the wordplay.
'debuts in' suggests taking the first letters (I've seen 'debut in' mean this).
The first letters of 'sydney this evening rocking expensive oboe' is 'STEREO'.
(Other definitions for stereo that I've seen before include "Sound - not mono" , "System that gives a three-dimensional sound" , "In-depth" , "System of sound reproduction" , "When sound comes through two channels" .)