The most common and most likely answer to this crossword clue is the 6 letter word PEBBLE
I've seen this crossword clue in Financial Times
P
E
B
B
L
E
More clues leading to the result PEBBLE
- Exercise gets first of bulky blokes losing eight stone
- Footballer collects books, one of many on beach
- B&B kept by former footballer – one by the sea?
- Unfinished request to get reflux set in stone
- Not a precious stone, but possibly worn
- Soft after exercise? Get fit, losing a stone
- Go out in suit, having lost a stone
- Football legend receives 2 billion for a small stone
Buddy explains!

The straight part
We know that "one by the sea" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one by the sea = pebble.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PEBBLE mean?
PEBBLE noun- A small stone, especially one rounded by the action of water.
- A particle from 4 to 64 mm in diameter, following the Wentworth scale.
- A small droplet of water intentionally sprayed on the ice that cause irregularities on the surface.
- Transparent and colourless rock crystal.
- A form of slow-burning gunpowder in large cubical grains.
- To pave with pebbles.
- To deposit water droplets on the ice.
- To give (leather) a rough appearance with small rounded prominences.
- To place a pebble at (a vertex of a graph) according to certain rules; see pebble game.