The most common and most likely answer to this crossword clue is the 5 letter word SHADY
S
H
A
D
Y
More clues leading to the result SHADY
- Gibe involving a daughter of doubtful honesty
- Sinister fish, ultimately nasty
- A duke in cast, underhand
- Doubtful, being kept somewhat in the dark?
- Dishonest, and wary about publicity
- Dodgy beer with lemonade has no source of nutrition
- Has dismissed deputy for being disreputable
- Cool but reserved restraining one's delight primarily
- District Attorney goes west, kidnapped by reticent suspect
Buddy explains!

The straight part
We know that "Sinister" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sinister = shady.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 SHADY mean?
SHADY adjective- Abounding in shades.
- Causing shade.
- Overspread with shade; sheltered from the glare of light or sultry heat.
- Not trustworthy; disreputable.
- Mean, cruel.