Sand (4)
I believe the answer is:
grit
'sand' is the definition.
(I know that sand can be written as grit)
This is all the clue.
(Other definitions for grit that I've seen before include "Courage (needed by chickens?)" , "Determination - small stones" , "Hard particles for firmness of character" , "Coarse stone or sand" , "lamb" .)