Stone fruit left out next to frozen water (6)
I believe the answer is:
pumice
'stone' is the definition.
(pumice is a kind of stone)
'fruit left out next to frozen water' is the wordplay.
'fruit left out' becomes 'pum' (I can't justify this - if you can you should believe this answer much more).
'next to' says to put letters next to each other.
'frozen water' becomes 'ice' (I've seen this before).
'pum'+'ice'='PUMICE'
Can you help me to learn more?
(Other definitions for pumice that I've seen before include "Mineral" , "Light porous stone used as polishing powder" , "Volcanic stone used as abrasive" , "Solidified lava used as an abrasive" , "Light form of solidified lava" .)