The most common and most likely answer to this crossword clue is the 10 letter word MONARCHIST
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More clues leading to the result MONARCHIST
- Upset stomach in the end for Burger King fan
- Royal supporter atop curved structure in thin fog
- Film rounding on leading Cavalier, perhaps?
- Playing it charms no Queen fan
- Unbridled anarchy disturbs drippy Queen fan perhaps
- Mac, in short, butchered for kingship
- Royalist doctor decapitated revolutionary
- New chief welcomed by tearful Queen fan
- Film takes against leading supporter of the royals
- Second in charts perhaps for Queen supporter
Buddy explains!

The straight part
We know that "supporter of the royals" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case supporter of the royals = monarchist.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 MONARCHIST mean?
MONARCHIST noun- An advocate of, or believer in, monarchy.