The most common and most likely answer to this crossword clue is the 6 letter word HELMET
I've seen this crossword clue in The Daily Telegraph
H
E
L
M
E
T
More clues leading to the result HELMET
- Protective wear Rachel half concealed on police force
- Endless inferno encountered in protective headgear
- What about this writer, wearing Lieutenant’s headgear!
- Protection for top Liberal theme following review?
- Kind of wood used in the odd piece of armour
- Protective wear brings endless assistance to London force
- 1 Down given leave to include Mike’s cover for 23
- Wood inside the plastic protective covering
- Satisfied after cure’s put paid to a nutcase
Buddy explains!

The straight part
We know that "protective covering" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case protective covering = helmet.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 HELMET mean?
HELMET noun- A protective head covering, usually part of armour.
- That which resembles a helmet in form, position, etc.
- To cover with, or as if with, a helmet.