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 am not sure about the 'gang' bit.
I cannot understand how the remainder of the clue works.
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" .)