Only small parts of them are seen above water (8)
I believe the answer is:
icebergs
'only small parts of them are seen above water' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for icebergs that I've seen before include "Masses of ice floating at sea" , "Large masses of frozen water" , "Masses of frozen water and lettuces" , "Only small parts can be seen above the water" , "Large masses of floating ice" .)