The most common and most likely answer to this crossword clue is the 9 letter word UNDERLING
I've seen this crossword clue in The Daily Telegraph
U
N
D
E
R
L
I
N
G
More clues leading to the result UNDERLING
Buddy explains!

The straight part
We know that "Lackey" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lackey = underling.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 UNDERLING mean?
UNDERLING noun- A subordinate, or person of lesser rank or authority.
- A low, wretched person.