Opening of audio track is going up (6)
I believe the answer is:
ascent
'is going up' is the definition.
(ascending means going up)
'opening of audio track' is the wordplay.
'opening of' says to take the initial letters.
'track' becomes 'scent' (both can mean a trace left by someone).
The first letter of 'audio' is 'a'.
'a'+'scent'='ASCENT'
(Other definitions for ascent that I've seen before include "Upwards motion" , "Upward journey" , "Going up" , "A rise in status; climb" , "Alpine expedition" .)