The most common and most likely answer to this crossword clue is the 4 letter word DUNE
I've seen this crossword clue in The Daily Telegraph
D
U
N
E
More clues leading to the result DUNE
- American’s sci-fi novel under construction: centre of Earth is missing!
- Film of a Parisian
- Stupid person about to get lost in mound of sand
- Dingy English seaside feature
- Fool caught out in mass of sand
- Charlie goes off with a fool to the sand ridge
- Halfwit caught flies in pile of sand
- Dark horse seen over eastern hill at coast?
Buddy explains!

The straight part
We know that "mound of sand" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mound of sand = dune.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 DUNE mean?
DUNE noun- A ridge or hill of sand piled up by the wind.