The most common and most likely answer to this crossword clue is the 8 letter word INCISORS
I
N
C
I
S
O
R
S
Buddy explains!
The straight part
We know that "Pieces of ivory guarded by canines that bite" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pieces of ivory guarded by canines that bite = incisors.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 INCISORS mean?
INCISORS noun- One of the front teeth of mammals, between the canines.