Lord Alfred Tennyson's poem "The Eagle" speaks to a dying eagle which falls into the sea beneath him. The poem is a short six line poem, broken into two stanzas. Each stanza is called a tercet (meaning three lines). The rhyme scheme is a simple rhyme scheme (aaa / bbb).
As for the line in question,
Ring'd with the azure world, he stands,
the line speaks to the halo of the blue sky which crowns the eagle. Azure means a bright blue color and ring'd refers to the way the sky encircles the eagle's head. Essentially, the eagle's head is crowned with the sky (showing his power and importance).
The pride of the eagle is inferred in the first few lines through the clasping of the crag with his crooked hands (personification). The eagle has come close to the sun in lands which are empty (alluding to those who leave when close to death). The importance of this lies in the "crowning" of the eagle, by the sky itself (the place where the eagle rules), and the royal color which encircles his head.