The most common and most likely answer to this crossword clue is the 8 letter word SWIMSUIT
I've seen this crossword clue in Independent
S
W
I
M
S
U
I
T
More clues leading to the result SWIMSUIT
- Limited coverage was initially breaking SIM cards of similar design
- Jam makers entering S&M clubs, perhaps in costume
- Cornwall – I first managed clubs, say
- Gearing for pool venture?
- Outfit for a butterfly?
- Item worn on divers occasions?
- Westminster lady has unlimited fun with sex in costume
- One piece, possibly alternative to sink, on trial
- Bathing outfit alternate saw film as nudist
Buddy explains!

The straight part
We know that "Outfit for a butterfly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case outfit for a butterfly = swimsuit.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 SWIMSUIT mean?
SWIMSUIT noun- A garment worn for swimming.
- A tight-fitting one-piece garment worn by women and girls.