The most common and most likely answer to this crossword clue is the 6 letter word FROCKS
F
R
O
C
K
S
More clues leading to the result FROCKS
Buddy explains!

The straight part
We know that "party attire?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case party attire? = frocks.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 FROCKS mean?
FROCKS noun- A dress, a piece of clothing for a female, which consists of a skirt and a cover for the upper body.
- An outer garment worn by priests and other clericals; a habit.
- A sailor's jersey.
- An undress regimental coat.
- A frog.