The most common and most likely answer to this crossword clue is the 5 plus 5 letter word BRASS TACKS
I've seen this crossword clue in The Guardian
B
R
A
S
S
T
A
C
K
S
More clues leading to the result BRASS TACKS
- The essentials in underwear piles
- Piles on underclothes one may get down to
- Business details underwear mountains
- Nitty-gritty of piles below underwear
- Essential stuff beginning to stink among piles of underwear?
- Nuts and bolts – they support a lot
- Items sold by M&S, piles — fundamental things for discussion
- Basic facts of loads beneath supporters?
- Supporters, lots getting hard facts
- Basic practicalities of supporters going to masses
Buddy explains!
The straight part
We know that "Basic facts" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case basic facts = brass tacks.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.