The most common and most likely answer to this crossword clue is the 4 plus 4 plus 4 letter word SHOT ONES BOLT
I've seen this crossword clue in The Times
S
H
O
T
O
N
E
S
B
O
L
T
Buddy explains!
The straight part
We know that "given too much too soon" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case given too much too soon = shot ones bolt.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.