The most common and most likely answer to this crossword clue is the 5 plus 2 plus 3 plus 5 letter word CLOSE TO THE CHEST
I've seen this crossword clue in The Guardian
C
L
O
S
E
T
O
T
H
E
C
H
E
S
T
Buddy explains!
The straight part
We know that "where one may 8/giving nothing away" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where one may 8/giving nothing away = close to the chest.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.