The most common and most likely answer to this crossword clue is the 8 letter word FRUMPISH
I've seen this crossword clue in Independent
F
R
U
M
P
I
S
H
More clues leading to the result FRUMPISH
- Swimmer covering bottom that’s not sexy?
- Shabby swimmer lagging behind
- Seek compliments about backside, becoming dowdy
- Badly-dressed seafood stuffed with cut of meat
- Search bottom parts, unattractive
- Low part embraced by bass, say — that’s plain
- Unattractive bottom pinched by swimmer
- Ill-dressed bum wearing mullet?
- Fairly drab Friday food? Bring in the meat!
Buddy explains!

The straight part
We know that "ill-dressed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ill-dressed = frumpish.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 FRUMPISH mean?
FRUMPISH adjective- Poorly dressed; wearing drab, lifeless, ill-fitting clothing, or being clothing of this kind.
- Bad-tempered.