Gang leaders sounding like a male quartet (7)
I believe the answer is:
foremen
'gang leaders' is the definition.
'foremen' can be an answer for 'leaders' (foreman is a kind of leader). I'm not certain of the 'gang' bit.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for foremen that I've seen before include "They are in charge of workmen" , "Gangers, supervisors" , "Persons in charge" , "Overseers" , "Resembling a bird" .)