The most common and most likely answer to this crossword clue is the 8 letter word QUINTAIN
Q
U
I
N
T
A
I
N
Buddy explains!
The straight part
We know that "Tilting post" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tilting post = quintain.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 QUINTAIN mean?
QUINTAIN noun- An object (generally a post or plank on a support) set up as a target to be tilted at in jousting, or otherwise used as target practice.