Floating ice chunk (4)
I believe the answer is:
berg
(Other definitions for berg that I've seen before include "Alban ----, composer of the incomplete opera 'Lulu' (1935)" , "Austrian composer of 12-tone music, d. 1935" , "South African mountain - Austrian composer" , "He composed" , "Alban -, composer (Wozzeck, Lulu)" .)