Greek harp (4)
I believe the answer is:
lyre
'greek harp' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for lyre that I've seen before include "Old instrument, like a harp" , "Ancient Greek harp" , "Old musical instrument with strings in U-shaped frame" , "Music-maker" , "Ancient musical instrument - sounds mendacious" .)