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

The straight part
We know that "reserved to an embarrassing degree" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reserved to an embarrassing degree = overbooked.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 OVERBOOKED mean?
OVERBOOKED verb- To sell or guarantee more seats for (an event) than actually exist.
- Having had more seats or tickets sold or guaranteed then were available.