According to the link this is from the Book of Lost Tales which means that it is a very early work of Tolkien's. I would describe it as "6 lines of verse"it is not a full sentence, nor is it a separate stanza or other separate section of the poem "The City of Present Sorrow" (Thank you Weather Vane for the link).
The full sentence is 8 lines or verse, specifically:
Thy thousand pinnacles and fretted spires
Are lit with echoes and lambent fires
Of many companies of bells that ring
Rousing pale visions of majestic days
The windy years have strewn down different ways;
And in thy walls still doth thy spirit sing
Songs of old memory amid thy present tears,
Or hope of days to come half-sad with many fears.
Note that verse in general often uses unusual grammatical forms to achieve mete and rhyme, as well as brevity (compressed meaning). Early verse by J.R.R. Tolkien in particular tends to use outdated forms and words, and unusual syntax. I do not advise a learner to imitate this verse as an example, much as I admire Tolkien's writing. All that said, I will attempt to recast the verse into prose, trying to preserve meaning.
[The unnamed city is being addressed as it it were a person] Your many towers are filled with lanterns and with echos of many bells. The ringing of those bells evokes dim images of past items of greatness which images the years have left along your various paths and streets. In your walls your spirit still sings songs which either recall old events, even as you cry from your current sadness, or else the songs express hope for the future, although that hope is saddened by many sources of fear.
I suspect, partly from references in other parts of the poem, and partly from what nI know of JRRT's history, that this is intended to be an image of Oxford during World War I. But I am not sure of that, and the question did not ask for literary analysis in any case. If there is remaining unclarity, please indicate this in a comment.