The most common and most likely answer to this crossword clue is the 6 letter word MERKIN
I've seen this crossword clue in Independent
M
E
R
K
I
N
Buddy explains!
The straight part
We know that "Hairpiece" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hairpiece = merkin.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 MERKIN mean?
MERKIN noun- A woman's pubic wig. Worn for nude stage appearances and by women, originally after shaving their pubic hair to eliminate lice or for other reasons, now often as a fashion item.
- A mop for cleaning cannon.
- The male counterpart of a beard, a companion to a lesbian to feign her straightness.
- An American.