Small stone particles (4)
I believe the answer is:
grit
'small stone particles' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for grit that I've seen before include "called for on icy roads" , "Bottle" , "Courage (needed by chickens?)" , "Coarse sandstone - strength of character" , "Small hard particles - determination" .)