The most common and most likely answer to this crossword clue is the 5 letter word DOTTY
I've seen this crossword clue in Financial Times
D
O
T
T
Y
More clues leading to the result DOTTY
- Bananas somewhat marked with spots
- Spotted bananas
- Somewhat eccentric, or mad, losing power to Democrat?
- Scatterbrained? In another case, I could be so described
- Barmy Sheila, very much so according to Morse
- Crazy like …
- Spotted cuckoo
- Wacky Races over . . . . wheels stopping . . . . . Dastardly gutted
- Busybody shopper, as originally depicted on TV? Triumphantly, yes
Buddy explains!

The straight part
We know that "Wacky" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case wacky = dotty.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 DOTTY mean?
DOTTY adjective- Mildly insane or eccentric; often, senile.
- Having an unsteady gait.
- A shotgun.
- Having many dots.