The most common and most likely answer to this crossword clue is the 12 letter word UNDERGARMENT
I've seen this crossword clue in The Daily Telegraph
U
N
D
E
R
G
A
R
M
E
N
T
More clues leading to the result UNDERGARMENT
- Perhaps slip down ahead of man carrying weapon
- Item of wear that’s never worn out
- Pants perhaps turned German off
- Item of clothing that’s never worn out
- Article that’s covered criminal armed gunner gets tense
- Merge and turn pants and vest?
- Angry German, getting covered, turned off hose?
- Garter men undo, endlessly excited finding stocking?
- Man grunted excitedly purchasing her topless teddy?
Buddy explains!

The straight part
We know that "Pants perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pants perhaps = undergarment.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 UNDERGARMENT mean?
UNDERGARMENT noun- Any garment worn underneath others, especially one worn next to the skin; an item of underwear.
- (in the plural) Temple garments worn by the followers of the Church of Jesus Christ of Latter-day Saints.