Beach grains (4)
'beach grains' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sand that I've seen before include "Result of rock erosion" , "Beach constituent" , "Yellow-brown colour" , "Granulated quartz" , "Hourglass contents" .)
(Other definitions for sands that I've seen before include "Rubs smooth" , "The Riddle of the . . . . . (novel by Erskine Childers)" , "Polishes (eg, wood)" , "They run out (of time)" , "You may see them by sea" .)