The most common and most likely answer to this crossword clue is the 3 plus 8 plus 4 letter word LIE DETECTOR TEST
I've seen this crossword clue in The Guardian
L
I
E
D
E
T
E
C
T
O
R
T
E
S
T
Buddy explains!
The straight part
We know that "It can locate position with match — true or false?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it can locate position with match — true or false? = lie detector test.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.