Coarse gravel (7)
I believe the answer is:
shingle
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">coarse gravel</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(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" .)