The most common and most likely answer to this crossword clue is the 11 letter word UNINHABITED
I've seen this crossword clue in The Times
U
N
I
N
H
A
B
I
T
E
D
More clues leading to the result UNINHABITED
Buddy explains!

The straight part
We know that "lifeless" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lifeless = uninhabited.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 UNINHABITED mean?
UNINHABITED adjective- Not inhabited; having no inhabitants