The most common and most likely answer to this crossword clue is the 7 letter word OKAYING
I've seen this crossword clue in The Times
O
K
A
Y
I
N
G
More clues leading to the result OKAYING
Buddy explains!

The straight part
We know that "giving thumbs-up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case giving thumbs-up = okaying.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 OKAYING mean?
OKAYING verb- To approve.
- To confirm by activating a button marked OK.