Scales not about to be seen in water at a beach (4)
I believe the answer is:
surf
'a beach' is the definition.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for surf that I've seen before include "White foam of breaking waves" , "Swell" , "Ride a wave" , "Ride the waves (or the Internet)" , "Waves breaking on the shore" .)