The most common and most likely answer to this crossword clue is the 7 letter word MAILING
I've seen this crossword clue in The Daily Telegraph
M
A
I
L
I
N
G
Buddy explains!
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 MAILING mean?
MAILING verb- (ditransitive) To send (a letter, parcel, etc.) through the mail.
- (ditransitive) To send by electronic mail.
- To contact (a person) by electronic mail.
- To arm with mail.
- To pinion.
- An act of sending mail.
- A farm.