The most common and most likely answer to this crossword clue is the 5 plus 5 letter word FANCY DRESS
I've seen this crossword clue in Financial Times
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More clues leading to the result FANCY DRESS
- Take a shine to groom in fun costume
- Like to line up disguise for ball?
- Deny scarf’s misplaced in party costume?
- Imagine groom’s costume
- Like the idea of force devoid of uniform or distinctive costume
- Like the look of doctorin party outfits
- Imagine pressure with no universal costume
- Desire clothing but not the ordinary sort
- What people wear during Halloween and kids contest
- Tend to like such a formal shirt perhaps as party wear?
Buddy explains!

The straight part
We know that "disguise for ball" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disguise for ball = fancy dress.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 FANCY DRESS mean?
FANCY DRESS noun- A costume, disguise to masquerade as something or someone else.
- Formalwear.