The most common and most likely answer to this crossword clue is the 3 letter word TAM
I've seen this crossword clue in The Times
T
A
M
Buddy explains!
The straight part
We know that "Scotch bonnet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case scotch bonnet = tam.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 TAM mean?
TAM noun- A type of woolen hat developed in Scotland, a toorie bunnet. Originally they were worn by both genders, but now they are mostly worn by men and boys.
- A traditional South and East Asian unit of weight, based upon the load of a shoulder pole and varying by place and over time but usually standardized at about 60 kg.