The most common and most likely answer to this crossword clue is the 7 letter word KNEEPAD
I've seen this crossword clue in The Guardian
K
N
E
E
P
A
D
More clues leading to the result KNEEPAD
Buddy explains!

The straight part
We know that "Protection" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case protection = kneepad.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 KNEEPAD mean?
KNEEPAD noun- A protective garment worn on a knee to protect it from injury, for example due to a blow or a fall.