Pebble (4)
'pebble' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stone that I've seen before include "Rag" , "Small rock" , "See 19" , "diamond, say" , "Kernel" .)
(Other definitions for rock that I've seen before include "Sweet < music" , "Pop; precious stone" , "startle" , "Seaside confectionery" , "Gently move; boulder" .)