Contents of hourglasses (5)
I believe the answer is:
sands
'contents of hourglasses' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sands that I've seen before include "You may see them by sea" , "Beach" , "The Riddle of the . . . . . (novel by Erskine Childers)" , "They run out (of time)" , "Smooths" .)