The most common and most likely answer to this crossword clue is the 9 letter word MESMERIZE
I've seen this crossword clue in Financial Times
M
E
S
M
E
R
I
Z
E
Buddy explains!
The straight part
We know that "Transfix" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case transfix = mesmerize.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 MESMERIZE mean?
MESMERIZE verb- To exercise mesmerism on; to affect another person, such as to heal or soothe, through the use of animal magnetism.
- To spellbind; to enthrall.