The most common and most likely answer to this crossword clue is the 8 letter word SANDBAGS
S
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Buddy explains!

The straight part
We know that "provide protection from enemy firing!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case provide protection from enemy firing! = sandbags.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 SANDBAGS mean?
SANDBAGS noun- A sturdy sack filled with sand, generally used in large numbers to make defensive walls against flooding, bullets, or shrapnel.
- A small bag filled with sand and used as a cudgel.
- An engraver's leather cushion, etc.
- A deceptive play whereby a player with a strong hand bets weakly or passively.