Coarse gravel (7)
I believe the answer is:
shingle
'coarse gravel' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for shingle that I've seen before include "Seaside pebbles" , "Small beach pebbles" , "English (anag)" , "A tile; some beach" , "Water-worn pebbles - roofing tile" .)