The most common and most likely answer to this crossword clue is the 6 letter word GROYNE
I've seen this crossword clue in The Times
G
R
O
Y
N
E
More clues leading to the result GROYNE
- Wood on the beach — no grey rocks
- Sea wall gone extremely rapidly in a storm
- Greek unit guards Yankee breakwater
- . No grey rocks in beach structure
- Bodily region said to be a barrier
- Engineering on grey hydraulic structure
- Mole appearing as grey on ground
- Mole‘s sensitive area under discussion
- Sexual centre discussed barrier method?
- Hero of the Rovers, amid retreating English, that stands against the tide
Buddy explains!

The straight part
We know that "breakwater" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case breakwater = groyne.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 GROYNE mean?
GROYNE noun- An often wooden structure that projects from a coastline to prevent erosion, longshore drift etc.; a breakwater.