The most common and most likely answer to this crossword clue is the 10 letter word POSTMASTER
I've seen this crossword clue in The Guardian
P
O
S
T
M
A
S
T
E
R
More clues leading to the result POSTMASTER
- Delivery supervisor behind mother bearing son
- Spar put in advertisement for e-mail manager
- Expert’s love for top American mailman?
- Large bill includes e.g. jigger for Oxford scholar
- Mail handler tore stamps apart
- One that’s organised stamp store?
- Eminent man of letters?
- Mail official reorganized sports team
- Working sort first off with stamps welcoming latest of clientele?
- Office head playing team sports
Buddy explains!

The straight part
We know that "Mail handler" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mail handler = postmaster.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 POSTMASTER mean?
POSTMASTER noun- The head of a post office.
- The administrator of an electronic mail system.
- A kind of scholar at Merton College, Oxford; portionist.
- One who has charge of a station for the accommodation of travellers; one who supplies post horses.