The most common and most likely answer to this crossword clue is the 6 letter word GANGES
I've seen this crossword clue in The Times
G
A
N
G
E
S
More clues leading to the result GANGES
- In Scotland go south, crossing eastern river
- Pack’s overtaking East Asian runner
- Jets and Sharks, say, crossing East River
- River in East — that’s crossed by crews
- Groups of workmen embracing oriental sacred flower
- River
- River swirling for example with problem getting across
- Group excursions after vacation in river
- An egg’s to be cooked in holy water
- River runs away from farmhouses
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 = ganges.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.