The most common and most likely answer to this crossword clue is the 10 letter word INCUBATION
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More clues leading to the result INCUBATION
Buddy explains!

The straight part
We know that "Brooding" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case brooding = incubation.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 INCUBATION mean?
INCUBATION noun- Sitting on eggs for the purpose of hatching young; a brooding on, or keeping warm, to develop the life within, by any process.
- The development of a disease from its causes, or the period of such development.
- A period of little reaction which is followed by more rapid reaction.
- One of the four proposed stages of creativity (preparation, incubation, illumination, and verification): the unconscious recombination of thought elements that were stimulated through conscious work at one point in time, resulting in novel ideas at a later point.
- Sleeping in a temple or other holy place in order to have oracular dreams or to receive healing.