Ocean floor (6)
I believe the answer is:
seabed
'ocean floor' is the definition.
(I know that ocean floor can be written as seabed)
This is all the clue.
(Other definitions for seabed that I've seen before include "The ocean floor, not for sleeping" , "marine base" , "Davy Jones's locker" , "Debase (anag)" , "Bottom of the ocean" .)