Breakaway choir master leaving one male group of musicians (9)
I believe the answer is:
orchestra
'group of musicians' is the definition.
(I've seen this before)
'breakaway choir master leaving one male' is the wordplay.
I cannot quite see how this works, but
'one' could be 'a' and 'a' is found within the answer.
'male' could be 'he' and 'he' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for orchestra that I've seen before include "A number of musicians" , "Large group of musicians" , "An assembly of musicians with various instruments" , "Instrumental group" , "Big group of musicians playing various instruments" .)