The most common and most likely answer to this crossword clue is the 9 letter word IMPLICATE
I've seen this crossword clue in The Guardian
I
M
P
L
I
C
A
T
E
More clues leading to the result IMPLICATE
- Involve one like Puck — a Celt, I suspect
- Involve mischief-maker with story about jazz fan
- Incriminate one politician, a whip involved in deceit
- Naughty boy — story about Tom maybe giving finger
- Involve troublemaker, one Conservative entering after time
- Involve mischievous child with tall story about pet
- Compromise one quietly involved in changing climate
- Reveal involvement of brat with deceit about pet
- Suggest involvement with malice and tip-off
Buddy explains!

The straight part
We know that "finger" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case finger = implicate.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 IMPLICATE mean?
IMPLICATE noun- The thing implied.
- (with “in”) To show to be connected or involved in an unfavorable or criminal way.
- To imply, to have as a necessary consequence or accompaniment.
- To imply without entailing; to have as an implicature.
- To fold or twist together, intertwine, interlace, entangle, entwine.