The most common and most likely answer to this crossword clue is the 5 plus 2 plus 3 plus 5 letter word ARMED TO THE TEETH
I've seen this crossword clue in The Guardian
A
R
M
E
D
T
O
T
H
E
T
E
E
T
H
More clues leading to the result ARMED TO THE TEETH
- Prepared for war theatre, MOD ordered choppers
- Generously equipped, like those prepared to bite back?
- Extremely well protected, with canine backing?
- Well protected, gumshield and all?
- Having many weapons, met death or explosive force
- Braced for conflict?
- Like savage warrior in bad dream as experienced by nippers?
- Flying to dam, three choppers fully equipped for battle
- How James Bond may be like Jaws?
- Having many weapons thereto met death in action
Buddy explains!
The straight part
We know that "Extremely well protected" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extremely well protected = armed to the teeth.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.