Composer Gustav (6)
I believe the answer is:
mahler
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">composer gustav</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for mahler that I've seen before include "Gustav -, Austrian symphonist" , "Gustav . . . . . ., Austrian composer" , "Austrian symphonic composer, d. 1911" , "Interrupt; hang" , "Austrian composer from Harlem?" .)