The most common and most likely answer to this crossword clue is the 3 plus 2 plus 7 letter word MAN OF LETTERS
I've seen this crossword clue in Financial Times
M
A
N
O
F
L
E
T
T
E
R
S
More clues leading to the result MAN OF LETTERS
Buddy explains!
The straight part
We know that "Academic/postman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case academic/postman = man of letters.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.