Floating ice mass (4)
I believe the answer is:
berg
'floating ice mass' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for berg that I've seen before include "Alban ----, composer of the incomplete opera 'Lulu' (1935)" , "One who scored" , "Large mass of floating ice" , "feature of icy waters" , "Mountain (in German, South African)" .)