Polar water formations (8)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
icebergs
(Other definitions for icebergs that I've seen before include "Masses of frozen water and lettuces" , "Arctic sea hazards" , "Large masses of floating ice" , "Frozen mountains in the sea" , "Only small parts can be seen above the water" .)