The most common and most likely answer to this crossword clue is the 4 plus 5 letter word JUST ABOUT
I've seen this crossword clue in Independent
J
U
S
T
A
B
O
U
T
Buddy explains!
The straight part
We know that "more likely outcome of 1A (‘jam tomorrow’ election promise)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more likely outcome of 1a (‘jam tomorrow’ election promise) = just about.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.