Planet's core hot from top to bottom (5)
I believe the answer is:
earth
'planet's' is the definition.
(Earth is an example)
'core hot from top to bottom' is the wordplay.
I cannot really understand how this works, but
'hot' could be 'h' (abbreviation eg on taps) and 'h' is found in the answer.
'from' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
The remaining letters 'art' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for earth that I've seen before include "costs so much?" , "our present abode" , "Solid ground" , "Soil; ground terminal" , "cost of which is very high" .)