Musician having ear most developed (7)
I believe the answer is:
maestro
'musician' is the definition.
(I have seen 'Expert musician' mean 'maestro' so perhaps 'musician' could also mean 'maestro')
'ear most developed' is the wordplay.
'developed' is an anagram indicator.
'ear'+'most'='earmost'
'earmost' with letters rearranged gives 'MAESTRO'.
'having' acts as a link.
(Other definitions for maestro that I've seen before include "Rattle, say" , "A master of any art, like music" , "Distinguished artist" , "Distinguished composer, conductor or performer" , "Eminent musician" .)