The most common and most likely answer to this crossword clue is the 9 letter word GEMINATED
I've seen this crossword clue in Financial Times
G
E
M
I
N
A
T
E
D
Buddy explains!

The straight part
We know that "paired up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case paired up = geminated.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 GEMINATED mean?
GEMINATED verb- To arrange in pairs.
- To occur in pairs.
- Of a consonant, pronounced longer and considered as being doubled; geminate.