The most common and most likely answer to this crossword clue is the 6 letter word PHONES
I've seen this crossword clue in The Guardian
P
H
O
N
E
S
More clues leading to the result PHONES
Buddy explains!
The straight part
We know that "Calls" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case calls = phones.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 PHONES mean?
PHONES noun- A device for transmitting conversations and other sounds in real time across distances, now often a small portable unit also capable of running software etc.
- To call (someone) using a telephone.
- A speech segment that possesses distinct physical or perceptual properties, considered as a physical event without regard to its place in the phonology of a language.
- Headphones