The most common and most likely answer to this crossword clue is the 4 plus 3 letter word ARAL SEA
A
R
A
L
S
E
A
More clues leading to the result ARAL SEA
- Body of water in addition almost filling region
- Asian disaster zone filled with mostly salt, dissolved
- Body of water, region covering a large space, primarily
- Body of water also deficient in region
- A lake, small in width as a waterbody
- Dar es Salaam demolished dams, removed from a water body
- Shrinking Asian lake further shortened in size
- Real as a shrunken body of water
- Region containing Albert’s shrunken lake
Buddy explains!

The straight part
We know that "water body" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case water body = aral sea.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.