Cruise sculptor's medium (3)
I believe the answer is:
ice
'cruise sculptor's medium' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ice that I've seen before include "Diamonds, colloquially" , "Cubes in a drink" , "Block" , "Diamonds (informal)" , "Being feeble, can't cut any" .)