A block destined for hot water (4,4)
I believe the answer is:
bath cube
'water' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see an association between them that I can't see?
'a block destined for hot' is the wordplay.
I cannot really understand how this works, but
'a' is found in the answer.
'block' could be 'cube' (cube is a kind of block) and 'cube' is found within the answer.
'hot' could be 'h' (abbreviation eg on taps) and 'h' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for bath cube that I've seen before include "Tub water softener" , "Block of salts for tub" , "relaxing salts" , "Die for a dip" .)