Answer:
In this excerpt from "The Lady of Shalott" by Alfred, Lord Tennyson, the synecdoche denotes confinement is Four gray walls and four gray towers
Explanation:
The question is not complete since it does not provide the excerpt. Here is the excerpt:
Willows whiten, aspens shiver.
The sunbeam showers break and quiver
In the stream that runneth ever
By the island in the river
Flowing down to Camelot.
Four gray walls, and four gray towers
Overlook a space of flowers,
And the silent isle imbowers
The Lady of Shalott.
Underneath the bearded barley,
The reaper, reaping late and early,
Hears her ever chanting cheerly,
Like an angel, singing clearly,
O'er the stream of Camelot.
Piling the sheaves in furrows airy,
Beneath the moon, the reaper weary
Listening whispers, ' 'Tis the fairy,
Lady of Shalott.'
A synecdoche is a literary device that refers to something by other words that are commonly related to their composition or common use in the context, the use of the color gray expresses sad and old things, it is a color of solitude, therefore gray walls do not only describe a sad situation but also a small and limited space which will be a good metaphor for confinement.