The most common and most likely answer to this crossword clue is the 4 letter word POND
I've seen this crossword clue in The Daily Telegraph
P
O
N
D
Buddy explains!
The straight part
We know that "water" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case water = pond.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 POND mean?
POND noun- An inland body of standing water, either natural or man-made, that is smaller than a lake.
- An inland body of standing water of any size that is fed by springs rather than by a river.
- The Atlantic Ocean. Especially in across the pond.
- To block the flow of water so that it can escape only through evaporation or seepage; to dam.
- To make into a pond; to collect, as water, in a pond by damming.
- To form a pond; to pool.
- To ponder.