Musical scale entertains curious bandleader (4-5)
I believe the answer is:
drum major
'bandleader' is the definition.
(I've seen this before)
'musical scale entertains curious' is the wordplay.
'musical scale' becomes 'dmajor' (I can't explain this - if you can you should give a lot more credence to this answer).
'entertains' indicates putting letters inside.
'curious' becomes 'rum' (synonyms).
'dmajor' placed around 'rum' is 'DRUM-MAJOR'.
Can you help me to learn more?
(Other definitions for drum major that I've seen before include "NCO in charge of military band" , "Non-commissioned officer in charge of part of a military band" , "Bandleader" , "Leader of a marching band" , "Occasional tosser in band" .)