The most common and most likely answer to this crossword clue is the 9 letter word DECEITFUL
I've seen this crossword clue in The Daily Telegraph
D
E
C
E
I
T
F
U
L
More clues leading to the result DECEITFUL
- Sneaky compiler enters deft clue, originally
- Fraudulent cutie fled in disarray
- Cute, if led astray, becoming two-faced
- Exceptionally deft clue I made up
- Unusually deft clue about one involved in fraud
- Lying revealed in deft clue I compiled
- Deft clue I composed to be misleading
- Deft clue I misjudged? It’s misleading
- When corrected, fetid clue is false
- Wasted futile month at first by lying
Buddy explains!

The straight part
We know that "Lying" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lying = deceitful.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 DECEITFUL mean?
DECEITFUL adjective- Deliberately misleading or cheating.
- Deceptive, two-faced.