Seaside (5)
I believe the answer is:
beach
'seaside' is the definition.
(a beach is found by the seaside)
This is the entire clue.
(Other definitions for beach that I've seen before include "Sloping part of shore" , "Accessible shoreline" , "Sand at the side of the sea" , "Stretch of coastline" , "Area of land sloping down to water" .)