The most common and most likely answer to this crossword clue is the 14 letter word RECONSTRUCTING
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More clues leading to the result RECONSTRUCTING
Buddy explains!

The straight part
We know that "building again" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case building again = reconstructing.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 RECONSTRUCTING mean?
RECONSTRUCTING verb- To construct again; to restore.
- To attempt to understand an event by recreating or talking through the circumstances.