The most common and most likely answer to this crossword clue is the 7 letter word DRAWBAR
I've seen this crossword clue in The Times
D
R
A
W
B
A
R
More clues leading to the result DRAWBAR
Buddy explains!
The straight part
We know that "Coupling" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case coupling = drawbar.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.
What does DRAWBAR mean?
DRAWBAR noun- An open-mouthed bar at the end of a car, which receives a coupling link and pin by which the car is drawn. It is usually provided with a spring to give elasticity to the connection between the cars of a train.
- A bar of iron with an eye at each end, or a heavy link, for coupling a locomotive to a tender or car.
- A device to couple a powered road vehicle to a load to transfer tractive effort to the load, either as a push or as a pull.
- A sliding bar on a Hammond organ, controlling the volume of a waveform.
- A device for changing the tools on milling machines.