The most common and most likely answer to this crossword clue is the 9 letter word EUPHRATES
E
U
P
H
R
A
T
E
S
More clues leading to the result EUPHRATES
- What about increased charges for running water?
- Perhaps post-Brexit tariffs restricting pub, of course, in Western Asia
- One running boozer beset by Brussels taxes?
- Reports of posh cargo on Stockton’s river
- Superheat boiling water
- What about high charges current in Middle East?
- 1 across risen, there’s a cuckoo circling
- Superheat liquid running water in SW Asia
- European Union measures to check acidity of river
- . He tears up, crying a river
Buddy explains!

The straight part
We know that "waterway" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case waterway = euphrates.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.