The most common and most likely answer to this crossword clue is the 3 plus 9 letter word ASH WEDNESDAY
I've seen this crossword clue in The Times
A
S
H
W
E
D
N
E
S
D
A
Y
More clues leading to the result ASH WEDNESDAY
- A quiet period assembling for a fast start
- Rubbish, burnt out team from 27 making a fast start
- Start to fast
- Dash newsy idea off wanting one to make fast start
- Quiet ways ended in turmoil after a fast start
- Lent beginner liquid dye and washes
- A fast start
- A quiet middle of the week gives time for reflection and penitence
- Was seedy hand out to have a fast time?
Buddy explains!
The straight part
We know that "fast time" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fast time = ash wednesday.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.