The most common and most likely answer to this crossword clue is the 3 letter word BAY
B
A
Y
More clues leading to the result BAY
Buddy explains!

The straight part
We know that "body of water" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case body of water = bay.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 BAY mean?
BAY noun- A berry.
- Laurus nobilis, a tree or shrub of the family Lauraceae, having dark green leaves and berries.
- Bay leaf, the leaf of this or certain other species of tree or shrub, used as a herb.
- (in the plural) The leaves of this shrub, woven into a garland used to reward a champion or victor; hence, fame, victory.
- A tract covered with bay trees.
- A kind of mahogany obtained from Campeche in Mexico.
- A body of water (especially the sea) more or less three-quarters surrounded by land.
- A bank or dam to keep back water.
- An opening in a wall, especially between two columns.
- An internal recess; a compartment or area surrounded on three sides.
- The distance between two supports in a vault or building with a pitched roof.
- Each of the spaces, port and starboard, between decks, forward of the bitts, in sailing warships.
- A bay platform.
- A bay window.
- The excited howling of dogs when hunting or being attacked.
- (by extension) The climactic confrontation between hunting-dogs and their prey.
- A state of being obliged to face an antagonist or a difficulty, when escape has become impossible.
- To howl.
- To bark at; hence, to follow with barking; to bring or drive to bay.
- To pursue noisily, like a pack of hounds.
- A brown colour/color of the coat of some horses.
- A horse of this color.
- Of a reddish-brown colour (especially of horses).