The most common and most likely answer to this crossword clue is the 9 letter word TELEGRAMS
I've seen this crossword clue in Financial Times
T
E
L
E
G
R
A
M
S
Buddy explains!
The straight part
We know that "communications" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case communications = telegrams.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 TELEGRAMS mean?
TELEGRAMS noun- A message transmitted by telegraph.
- To send a telegram.
- To send a telegram to (a person).
- To send (a message) in a telegram.