Philosopher quietly left at end of concerto (5)
I believe the answer is:
plato
'philosopher' is the definition.
(Plato is an example)
'quietly left at end of concerto' is the wordplay.
'quietly' becomes 'p' (p for piano and quiet).
'left' becomes 'l' (common abbreviation).
'end of' suggests the final letters.
The last letter of 'concerto' is 'o'.
'p'+'l'+'at'+'o'='PLATO'
(Other definitions for plato that I've seen before include "Greek philosopher, disciple of Aristotle" , "To pal up with Greek philosopher" , "Ancient Athenian philosopher, pupil of Socrates" , "Teacher of Aristotle, pupil of Socrates" , "Greek character" .)