The most common and most likely answer to this crossword clue is the 5 plus 2 plus 4 letter word PANTS ON FIRE
I've seen this crossword clue in The Guardian
P
A
N
T
S
O
N
F
I
R
E
Buddy explains!
The straight part
We know that "due to too much lying?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case due to too much lying? = pants on fire.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.