Complete musical ability to charm (6)
I believe the answer is:
endear
'to charm' is the definition.
(I've seen this in another clue)
'complete musical ability' is the wordplay.
'complete' becomes 'end' (I've seen this in another clue).
'musical ability' becomes 'ear' (I've seen this in another clue).
'end'+'ear'='ENDEAR'
(Other definitions for endear that I've seen before include "Win over" , "Arouse affection" , "Delight - please" , "Make prized" , "Neared so as to make loved" .)