When Hank tells Clarence that he "ain't more than a paragraph," is he being sarcastic?

The quote that you are referring to comes in the second chapter
of this highly amusing story. Hank, having been transported back to Arthurian times, still
doesn't know where he is or in what time, and he assumes that he is in some kind of mental
asylum. He sees Clarence come up to him and Clarence informs Hank of his station and job in this
world:

He was pretty
enough to frame. He arrived, looked me over with a smiling and impudent curiosity; said he had
come for me, and informed me that he was a
page.

Of course, the response you have
quoted lies on deliberate pun that Hank is making. He is ignoring the definition of the word that
Clarence is using, referring to his job in court, and deliberately misinterpreting it to mean a
page of a book. Thus, his response shows how unimpressed Hank is with Clarence and his
appearance, using sarcasm to suggest that Clarence is actually a lot less than what he thinks he
is - just "a paragraph."