Piece of wood: heavy weight that floats in the sea (8)
I believe the answer is:
plankton
'floats in the sea' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'piece of wood heavy weight' is the wordplay.
'piece of wood' becomes 'plank'.
'heavy weight' becomes 'ton' (a ton weighs a lot).
'plank'+'ton'='PLANKTON'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for plankton that I've seen before include "Microscopic sea food" , "Microscopic organisms in seawater" , "Food source for aquatic creatures" , "Microscopic organic life that floats in sea" , "Tiny creatures" .)