Ice mass (4)
I believe the answer is:
berg
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">ice mass</span>' is the definition.<br/ ><span class="explanation-format__explanation">(berg is a kind of ice mass)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for berg that I've seen before include "Lump of ice" , "He composed" , "feature of icy waters" , "Alban ----, composer of the incomplete opera 'Lulu' (1935)" , "ice in the drink" .)