The most common and most likely answer to this crossword clue is the 6 letter word THAMES
I've seen this crossword clue in Financial Times
T
H
A
M
E
S
More clues leading to the result THAMES
- What has London banks acting badly during trial, mostly
- Morning in the sticks, for starters
- Engineer has met capital banker
- River Tees engulfing northern home
- Not wild about hotel beside small river
- River quietens after introduction of hydrant
- Feature of London breaks: bagging husband!
- River seen from a motorway in the south
- Current actor in rising TV shows
- Flat’s sheltering drug runner
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 = thames.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.