The most common and most likely answer to this crossword clue is the 5 plus 4 letter word EVERY INCH
I've seen this crossword clue in The Guardian
E
V
E
R
Y
I
N
C
H
More clues leading to the result EVERY INCH
- Extremely fashionable viewed in mirror, almost entirely
- All in? Completely!
- Completely exquisite first light over island
- A German child assimilating so thoroughly
- What keeps well, incorporated thoroughly?
- Wholly appropriate in niche manufacture
- Completely and remarkably weird niche trousers
- What inspires remarkably popular leader of community totally
- Quite so in a German church
Buddy explains!

The straight part
We know that "Completely" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case completely = every inch.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.