Sole broken by hard beach stones (7)
I believe the answer is:
shingle
'beach stones' is the definition.
'sole broken by hard' is the wordplay.
'sole' becomes 'single' ('single' can be a synonym of 'sole').
'broken by' means one lot of letters goes inside another.
'hard' becomes 'h'.
'single' enclosing 'h' is 'SHINGLE'.
(Other definitions for shingle that I've seen before include "English (anag)" , "Small worn stones and pebbles on the shore" , "Gravelly composition" , "Loose stones" , "Coarse gravel (on beach)" .)