The most common and most likely answer to this crossword clue is the 2 letter word HA
I've seen this crossword clue in The Daily Telegraph
H
A
More clues leading to the result HA
- Feature of landscape gardens comprising two hectares
- Landscape feature of two hectares
- Boundary marker set in ditch? Very funny!
- Had old money dropped repeatedly in ditch
- A hotel doubled up with laughter
- It won’t be seen as a boundary
- Hearts, represented by ace, laid down twice for a laugh
- You could make a hash of onomatopoeic sounds of laughter
- Laughter concealed depression
- Boundary in park comprising two hectares
Buddy explains!

The straight part
We know that "ditch" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ditch = ha.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 HA mean?
HA interjection- A representation of laughter.
- An exclamation of triumph or discovery.
- An exclamation of grief.
- A sound of hesitation: er, um.
- Said when making a vigorous attack.