Icy hazard at sea (4)
I believe the answer is:
'icy hazard at sea' 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 "Mountain (in German, South African)" , "trouble at sea" , "African mount" , "Large mass of floating ice" , "feature of icy waters" .)