The most common and most likely answer to this crossword clue is the 14 letter word CURTAIN-RAISER
I've seen this crossword clue in The Times
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More clues leading to the result CURTAIN-RAISER
Buddy explains!
The straight part
We know that "Beginner" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case beginner = curtain-raiser.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 CURTAIN-RAISER mean?
CURTAIN-RAISER noun- In a theater, an initial play, musical performance, etc which precedes the main performance.
- (by extension) A prelude or introduction to an activity or thing.