The most common and most likely answer to this crossword clue is the 7 letter word MAXILLA
I've seen this crossword clue in The Guardian
M
A
X
I
L
L
A
More clues leading to the result MAXILLA
Buddy explains!

The straight part
We know that "Jaw" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jaw = maxilla.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 MAXILLA mean?
MAXILLA noun- Either of the two bones that together form the upper jaw.
- (arthropodology) One of a set of paired mouthparts found in many arthropods and used for tasting and manipulating food.