The most common and most likely answer to this crossword clue is the 5 letter word RHINE
I've seen this crossword clue in The Guardian
R
H
I
N
E
More clues leading to the result RHINE
- Polish right for small flower
- Short African mammal by eastern river
- River runs within explosive borders
- Right height in English river
- River rising high in northern Europe, initially
- About to capture hydrogen in river
- Arch-fiend not oddly associated with East European banker
- Tossed her in river
- Horned beast losing oxygen and energy in river
- Nefertiti’s fifth husband at home by English river
Buddy explains!
The straight part
We know that "river" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case river = rhine.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.