Cube (4)
'cube' is the definition.
(I know that dice is a type of cube)
This is the entire clue.
(Other definitions for dice that I've seen before include "Gaming cube(s)" , "Small cube" , "Make into chips" , "Gambling items" , "Random number generators" .)
(Other definitions for root that I've seen before include "essential nature" , "Part of plant drawing nutrients from soil" , "Rhizome" , "Source; firmly establish" , "Origin; carrot perhaps" .)
(Another definition for hexahedron that I've seen is " A figure".)
'cube' is the definition.
(die is a kind of cube)
This is all the clue.
(Other definitions for die that I've seen before include "Pass away" , "Give out" , "a block?" , "Depart with engraved stamp" , "Craps cube" .)