The most common and most likely answer to this crossword clue is the 4 plus 3 plus 3 letter word DOTS THE I’S
I've seen this crossword clue in The Guardian
D
O
T
S
T
H
E
I
â
€
™
S
Buddy explains!
The straight part
We know that "Is exact in detailing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case is exact in detailing = dots the i’s.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.