The most common and most likely answer to this crossword clue is the 4 plus 3 plus 6 letter word SLAP AND TICKLE
I've seen this crossword clue in The Guardian
S
L
A
P
A
N
D
T
I
C
K
L
E
More clues leading to the result SLAP AND TICKLE
Buddy explains!

The straight part
We know that "it!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it! = slap and tickle.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.