The most common and most likely answer to this crossword clue is the 7 letter word COUPLER
I've seen this crossword clue in Financial Times
C
O
U
P
L
E
R
Buddy explains!
The straight part
We know that "It unites" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it unites = coupler.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 COUPLER mean?
COUPLER noun- Someone who couples things together, especially someone whose job it is to couple railway carriages.
- Anything that serves to couple things together; but especially a device that couples railway carriages.
- A device that connects two keyboards of an organ together so that they play together.
- A device used to convert electronic information into audible sound signals for transmission over telephone lines.
- An electrical device used to transfer energy from one electric device to another, especially without a physical connection.