The most common and most likely answer to this crossword clue is the 7 letter word COOKING
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More clues leading to the result COOKING
Buddy explains!

The straight part
We know that "preparing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case preparing = cooking.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 COOKING mean?
COOKING verb- To prepare (food) for eating by heating it, often by combining it with other ingredients.
- To prepare (unspecified) food for eating by heating it, often by combining it with other ingredients.
- To be cooked.
- To be uncomfortably hot.
- To execute by electric chair.
- To hold onto (a grenade) briefly after igniting the fuse, so that it explodes almost immediately after being thrown.
- To concoct or prepare.
- To tamper with or alter; to cook up.
- To play or improvise in an inspired and rhythmically exciting way. (From 1930s jive talk.)
- To play music vigorously.
- To make the noise of the cuckoo.
- To throw.
- The process of preparing food by using heat.
- An instance of preparing food by using heat.
- The result of preparing food by using heat.
- In progress, happening.