Musician's harp's kept tuned slightly higher than usual (5)
I believe the answer is:
sharp
'musician's' is the definition.
(I have seen 'British musician' mean 'sharp' so perhaps 'musician' could also mean 'sharp')
'harp's kept tuned slightly higher than usual' is the wordplay.
'harp's' anagrams to 'SHARP'.
But, I am not clear how this is indicated.
Can you help me to learn more?
(Other definitions for sharp that I've seen before include "Liable to cut" , "Acute - very keen" , "exactly on time" , "Unscrupulous character" , "tart" .)