The most common and most likely answer to this crossword clue is the 10 letter word INSIDE-OUT
I've seen this crossword clue in The Times
I
N
S
I
D
E
-
O
U
T
Buddy explains!
The straight part
We know that "Completely/reversed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case completely/reversed = inside-out.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.
What does INSIDE-OUT mean?
INSIDE-OUT adverb- With the inside surface turned to be on the outside.
- (of knowledge) Thoroughly, extremely well.
- Describes the hitting of a ball that pitched outside of leg stump to the off side of the field.
- With the inner and outer surfaces reversed.
- Describing cross-court shots made by the unexpected hand, as of a backhand return of a ball struck to the player's forehand.
- Directed to the side; sideways.
- Slanting or sloping; oblique.
- Indirect; suggestive; not straightforward.
- Along the side of something.