Blow wind instrument holding top notes (6)
I believe the answer is:
bungle
'blow' is the definition.
(to blow something is to bungle or ruin it)
'wind instrument holding top notes' is the wordplay.
'wind instrument' becomes 'bugle' (bugle is a kind of wind instrument).
'holding' means one lot of letters goes inside another.
'top notes' becomes 'n' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'bugle' going around 'n' is 'BUNGLE'.
Can you help me to learn more?
(Other definitions for bungle that I've seen before include "Botch, make a hames of" , "Badly handle" , "(Make an) embarrassing mistake" , "Do something carelessly or badly" , "Botch; failure" .)