Waves breaking on the shore (4)
I believe the answer is:
surf
'waves breaking on the shore' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for surf that I've seen before include "Use the Internet" , "Foam from breakers" , "to maintain one's standing on board?" , "Foam formed by breaking waves" , "Ride a wave" .)