The most common and most likely answer to this crossword clue is the 7 letter word ILLICIT
I've seen this crossword clue in The Times
I
L
L
I
C
I
T
More clues leading to the result ILLICIT
- I caught it sitting by sick criminal
- Criminal Roman pair, seizing £50, back out of town
- Suffering? Current back spasm ruled out
- One entering seedy clubs, getting it wrong
- I caught it sitting next to poorly criminal
- What’s permissible to the Italian – isn’t!
- In hearing, bring forth criminal
- Incompetent appeal collecting very little money in NY without permission
- Poorly lit centre of most of main town’s criminal
- Banned guilds policed city centres
Buddy explains!

The straight part
We know that "Criminal" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case criminal = illicit.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 ILLICIT mean?
ILLICIT noun- A banned or unlawful item.
- Not approved by law, but not invalid.
- Breaking social norms.
- Unlawful.