The most common and most likely answer to this crossword clue is the 10 plus 3 letter word GENERATION GAP
I've seen this crossword clue in The Times
G
E
N
E
R
A
T
I
O
N
G
A
P
Buddy explains!
The straight part
We know that "What could make teen go wild with Gran, pa and I?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what could make teen go wild with gran, pa and i? = generation gap.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.