The most common and most likely answer to this crossword clue is the 8 letter word SEASHORE
I've seen this crossword clue in The Times
S
E
A
S
H
O
R
E
More clues leading to the result SEASHORE
- A small house in dry coastal region
- Shoes are awkward where there could be sand
- Fish moving up a southern coastline
- Audibly recognise certain beach
- Vexed about European tree such as beech, from what we hear
- Beach ‘shoes’ are flip-flops!
- Beach shoes are adjusted for it
- Heroes running around when there are shells here?
- Strand in a quiet, alternatively secluded spot
- Beach shoes are discarded
Buddy explains!

The straight part
We know that "coastline" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coastline = seashore.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 SEASHORE mean?
SEASHORE noun- The coastal land bordering a sea or an ocean.
- The foreshore, the strip of land between low water and high water.