The friar doesn't look much like we would probably expect a friar to look. Since friars are supposed to live in poverty, Chaucer's friar is definitely not a typical friar.
I'll indicate the portions of the friar's prologue which directly address his appearance here:
His throat was white as lily of the May;
Yet strong he was as any champion.
A white neck was thought to be a sign of a loose or immoral person during Chaucer's time.
For he was not like a cloisterer,(50)
With threadbare cope as is the poor scholar,
But he was like a lord or like a pope.
Of double worsted was his semi-cope,
That rounded like a bell, as you may guess.
He lisped a little, out of wantonness,(55)
To make his English soft upon his tongue;
And in his harping, after he had sung,
His two eyes twinkled in his head as bright
As do the stars within the frosty night.
This worthy limiter was named Hubert.
In this section, the narrator describes the Friar's dress. He states that the friar is not dressed plainly in "threadbare" clothing as one would expect, but more like an elite member of the clergy. He compares his cloak to a bell, implying that it is both large and elaborate.
The Friar is also described as trying to make his English sound pretty by modifying his voice. Even though this is not physical appearance, it still indicates an aspect of his character- that he wants to be percieved as pleasant and pretty.