Sadly alto dies alone (8)
I believe the answer is:
isolated
'alone' is the definition.
(similar in meaning)
'sadly alto dies' is the wordplay.
'sadly' indicates anagramming the letters.
'alto'+'dies'='altodies'
'altodies' anagrammed gives 'ISOLATED'.
(Other definitions for isolated that I've seen before include "Remote; lonely" , "Off the beaten track" , "'Detached, kept apart (8)'" , "Segregated" , "Alone, apart, detached" .)