The most common and most likely answer to this crossword clue is the 4 plus 4 plus 7 letter word LOCH NESS MONSTER
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More clues leading to the result LOCH NESS MONSTER
- Head in new school term organised rarely seen tourist attraction
- Has this ever been seen as a Scottish tourist attraction?
- Apparition left Scots horsemen rattled as knight invades
- Cast net — Holmes scorns a chimera?
- Reportedly catch head of huge mythical creature
- Solemn sect shorn for battle — a fabled phenomenon?
- Helen scorns most changes, not one has been seen yet
- Legendary swimmer left Scots horsemen at sea around noon
- Dubious Scotsmen’s lore about thing periodically seen?
Buddy explains!

The straight part
We know that "Legendary/swimmer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case legendary/swimmer = loch ness monster.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.