The most common and most likely answer to this crossword clue is the 3 plus 2 plus 6 letter word GET IT ACROSS
I've seen this crossword clue in The Guardian
G
E
T
I
T
A
C
R
O
S
S
More clues leading to the result GET IT ACROSS
Buddy explains!

The straight part
We know that "explain the idea properly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case explain the idea properly = get it across.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.