The most common and most likely answer to this crossword clue is the 4 plus 4 plus 4 letter word MAKE ONES MOVE
I've seen this crossword clue in The Times
M
A
K
E
O
N
E
S
M
O
V
E
More clues leading to the result MAKE ONES MOVE
Buddy explains!
The straight part
We know that "Leave a crossroads/transfer from A2 to A3?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leave a crossroads/transfer from a2 to a3? = make ones move.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.