The most common and most likely answer to this crossword clue is the 14 letter word PREDISPOSITION
I've seen this crossword clue in The Times
P
R
E
D
I
S
P
O
S
I
T
I
O
N
More clues leading to the result PREDISPOSITION
Buddy explains!

The straight part
We know that "Penchant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case penchant = predisposition.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 PREDISPOSITION mean?
PREDISPOSITION noun- The state of being predisposed or susceptible to something, especially to a disease or other health problem