The most common and most likely answer to this crossword clue is the 3 plus 8 plus 2 letter word PUT EMPHASIS ON
P
U
T
E
M
P
H
A
S
I
S
O
N
Buddy explains!
The straight part
We know that "highlight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case highlight = put emphasis on.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.