The most common and most likely answer to this crossword clue is the 10 letter word PORTCULLIS
I've seen this crossword clue in The Daily Telegraph
P
O
R
T
C
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L
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S
More clues leading to the result PORTCULLIS
- Left is holding thinning out operation which blocks entrants
- Grating remark added to letter about criminal court badly set up
- Left on board, gather one’s entry may be barred by this
- Surplus selection is kept under wine bar on the way in
- Keep barrier in harbour — copper is checking lines
- Gather below Dover perhaps is castle entrance
- Keep barrier in island on hold, and gather within
- Scroll I put out showing symbol of Parliament
- Removal of creatures from harbour is a defensive measure
- It bars the entrance to unwanted visitors
Buddy explains!
The straight part
We know that "castle ent" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case castle ent = portcullis.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 PORTCULLIS mean?
PORTCULLIS noun- A gate in the form of a grating which is lowered into place at the entrance to a castle, fort, etc.
- An English coin of the reign of Elizabeth I, struck for the use of the East India Company, and bearing the figure of a portcullis on the reverse.
- To obstruct with, or as with, a portcullis; to shut; to bar.