The most common and most likely answer to this crossword clue is the 3 plus 3 letter word BIG BEN
B
I
G
B
E
N
More clues leading to the result BIG BEN
- Where to see the time ebbing away
- Landmark of our island visible in … well, in Paris
- It gives time to see large mountain
- Bell‘s major feature of Scotch scene
- Thamesside tower etc, British, being restored
- Being upset by British striker at Westminster
- Bell made by Britain wearing well in Paris
- To regularly bring a bong around end of House?
- Striker’s great tendency to finish early
- Clock whopping bill that’s picked up
Buddy explains!

The straight part
We know that "Landmark" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case landmark = big ben.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.