Interval: time one's wasted (8)
I believe the answer is:
semitone
'interval' is the definition.
(semitone is a kind of interval)
'time one's wasted' is the wordplay.
'wasted' indicates anagramming the letters.
'time'+'ones'='timeones'
'timeones' with letters rearranged gives 'SEMITONE'.
(Other definitions for semitone that I've seen before include "Minimum interval in diatonic scale" , "Small interval between notes" , "Short musical interval" , "One twelfth of an octave" , "100 cents" .)