The most common and most likely answer to this crossword clue is the 8 letter word POSTCARD
P
O
S
T
C
A
R
D
More clues leading to the result POSTCARD
- Message sent from holiday job by Joker, perhaps
- Job Jack possibly pursues - one with seaside prospects?
- Brief message: retired doctor performs operation
- Petty Officer’s time with Jack maybe? Write home about it on this?
- . Brief note following list of runners
- One bearing message whose view is one-sided?
- Message illustrated by character going after job
- Job with club for instance providing communication
- Form of communication appearing briefly in Snapchat
- One-sided view from a correspondent?
Buddy explains!

The straight part
We know that "piece of mail" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case piece of mail = postcard.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 POSTCARD mean?
POSTCARD noun- A rectangular piece of thick paper or thin cardboard intended to be written on and mailed without an envelope. In the case of a picture postcard one side carries a picture or photograph.
- To send a postcard to.
- To send by means of a postcard.