The most common and most likely answer to this crossword clue is the 11 letter word GAMEKEEPERS
I've seen this crossword clue in The Times
G
A
M
E
K
E
E
P
E
R
S
More clues leading to the result GAMEKEEPERS
Buddy explains!

The straight part
We know that "workers on estate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case workers on estate = gamekeepers.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 GAMEKEEPERS mean?
GAMEKEEPERS noun- A person employed to maintain the game for hunting and all associated materials and effects. Often shortened to keeper.