The most common and most likely answer to this crossword clue is the 7 letter word TOSSERS
I've seen this crossword clue in Independent
T
O
S
S
E
R
S
Buddy explains!

The straight part
We know that "On Shrove Tuesday, cooks might be these/sorts of idiots" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case on shrove tuesday, cooks might be these/sorts of idiots = tossers.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 TOSSERS mean?
TOSSERS noun- One who tosses or throws something.
- A male who masturbates.
- An objectionable male, often somewhat obnoxious in demeanour.
- A program that forwards or redirects messages on a bulletin board system.