The most common and most likely answer to this crossword clue is the 9 letter word EXCHANGES
I've seen this crossword clue in The Guardian
E
X
C
H
A
N
G
E
S
Buddy explains!
The straight part
We know that "Calls may be made via these/money markets" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case calls may be made via these/money markets = exchanges.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 EXCHANGES mean?
EXCHANGES noun- An act of exchanging or trading.
- A place for conducting trading.
- A telephone exchange.
- The fourth through sixth digits of a ten-digit phone number (the first three before the introduction of area codes).
- A conversation.
- The loss of one piece and associated capture of another
- The thing given or received in return; especially, a publication exchanged for another.
- The transfer of substances or elements like gas, amino-acids, ions etc. sometimes through a surface like a membrane.
- The difference between the values of money in different places.