"Rocks" in a tumbler (3)
I believe the answer is:
ice
'rocks in a tumbler' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ice that I've seen before include "Cooler" , "Cold stuff used in enticement" , "Frozen liquid" , "Skating surface" , "Girl's best friends" .)