The most common and most likely answer to this crossword clue is the 5 letter word TABOO
I've seen this crossword clue in The Times
T
A
B
O
O
More clues leading to the result TABOO
- Volunteers express disapproval — that’s not acceptable
- Key rings unable to be brought up
- Banned volunteers voice displeasure
- Cheers and jeers largely disapproved of
- Bill loves what’s prohibited
- Disapproved of denouement, a book's essential part?
- Ban makeshift boat heading for ocean
- Forbidden book, not acceptable in Chinese philosophy
- Check balls out
- Ban cheers and a more hostile expression
Buddy explains!

The straight part
We know that "Disapproved of" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case disapproved of = taboo.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 TABOO mean?
TABOO noun- An inhibition or ban that results from social custom or emotional aversion.
- (in Polynesia) Something which may not be used, approached or mentioned because it is sacred.
- To mark as taboo.
- To ban.
- To avoid.
- Excluded or forbidden from use, approach or mention.
- Culturally forbidden.