The most common and most likely answer to this crossword clue is the 10 letter word UNANIMATED
U
N
A
N
I
M
A
T
E
D
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 = unanimated.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 UNANIMATED mean?
UNANIMATED adjective- Inanimate.
- Not animated; lacking vivacity.