Flintstone, or smaller stones (7)
I believe the answer is:
pebbles
'stones' is the definition.
(pebble is a kind of stone)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for pebbles that I've seen before include "Small round stones, as on beach" , "Small rounded stones" , "Small, smooth, rounded rocks" .)