Botch at least three notes (5)
I believe the answer is:
misdo
'botch' is the definition.
(I've seen this in another clue)
'at least three notes' is the wordplay.
'at' means one lot of letters go next to another.
'least three' becomes 'do' (I can't explain this - if you can you should believe this answer much more).
'notes' becomes 'mis' (more than one mi, a musical note).
'do' after 'mis' is 'MISDO'.
Can you help me to learn more?
(Other definitions for misdo that I've seen before include "Perform improperly" , "Perform wrongly" .)