The most common and most likely answer to this crossword clue is the 11 letter word PRELIMINARY
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More clues leading to the result PRELIMINARY
Buddy explains!

The straight part
We know that "First" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case first = preliminary.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 PRELIMINARY mean?
PRELIMINARY noun- A preparation for a main matter; an introduction.
- Any of a series of sports events that determine the finalists
- A relatively minor contest that precedes a major one, especially in boxing
- In preparation for the main matter; initial, introductory, preparatory.