The most common and most likely answer to this crossword clue is the 1 plus 10 plus 3 letter word A SHROPSHIRE LAD
I've seen this crossword clue in Financial Times
A
S
H
R
O
P
S
H
I
R
E
L
A
D
Buddy explains!
The straight part
We know that "his major work" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case his major work = a shropshire lad.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.