Choir leader leaving musical composition without a name (4)
I believe the answer is:
anon
'choir leader' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'musical composition without a name' is the wordplay.
I cannot quite understand how this works, but
'without' could be 'no' and 'no' is located in the answer.
'a' could be 'an' and 'an' is present in the answer.
This accounts for all the letters.
This may be the basis of clue (or it may be nonsense).
'leaving' acts as a link.
(Other definitions for anon that I've seen before include "Some time soon" , "soon to be written" , "At another time and with no identity, in short" , "Writer unknown" , "Of unknown name (abbr)" .)