Mafia leader's way of raising the tone? (4)
I believe the answer is:
capo
'mafia leader's' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for capo that I've seen before include "something to grip neck tightly" , "Leader of gang" , "Gangster boss" , "Mafia leader" , "Head honcho in Cosa Nostra" .)