Composer from Harlem (6)
I believe the answer is:
mahler
'composer' is the definition.
(Gustav Mahler)
'from harlem' is the wordplay.
'from' is an anagram indicator (from the letters).
'harlem' anagrammed gives 'MAHLER'.
(Other definitions for mahler that I've seen before include "Austrian composer from Harlem?" , "Austrian symphonic composer, d. 1911" , "Gustav -, Austrian symphonist" , "Lift" , "Vienna and New York opera conductor" .)