Almost beyond heartless nut (6)
I believe the answer is:
almond
'nut' is the definition.
(almond is a type of nut)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for almond that I've seen before include "Nut which provides cake icing" , "Type of nut" , "Yellowish brown" , "Fruit kernel of a peach-related tree" , "Nut (tree)" .)