The most common and most likely answer to this crossword clue is the 11 letter word STABLE-MATE
S
T
A
B
L
E
-
M
A
T
E
Buddy explains!
The straight part
We know that "he works where horses are put up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case he works where horses are put up = stable-mate.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.