The most common and most likely answer to this crossword clue is the 9 letter word SPILLIKIN
I've seen this crossword clue in The Guardian
S
P
I
L
L
I
K
I
N
Buddy explains!
The straight part
We know that "Jack Straw?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jack straw? = spillikin.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 SPILLIKIN mean?
SPILLIKIN noun- One of the straws (or small pieces of wood, ivory, etc.) used in the game of jackstraws or spillikins.