The most common and most likely answer to this crossword clue is the 5 letter word TABUS
I've seen this crossword clue in Financial Times
T
A
B
U
S
Buddy explains!

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 TABUS mean?
TABUS 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.