Question

Which line in this excerpt from act I, scene I, of Richard III is a stage direction?
RICHARD III (Duke of Gloucester):
. . . And if King Edward be as true and just
As I am subtle, false and treacherous,
This day should Clarence closely be mew'd up,
About a prophecy, which says that 'G'
Of Edward's heirs the murderer shall be.
Dive, thoughts, down to my soul: here
Clarence comes.
(Enter CLARENCE, guarded, and BRAKENBURY)
Brother, good day; what means this armed guard
That waits upon your grace?

GEORGE PLANTAGENET (Duke of Clarence): His majesty
Tendering my person's safety, hath appointed
This conduct to convey me to the Tower.

RICHARD III (Duke of Gloucester): Upon what cause?

Answer 1

The stage direction is the "(Enter CLARENCE, guarded, and BRAKENBURY)
I don't want to give a specific number because I'm afraid on paper the lines are probably showed differently, but you can count to it! Good luck :)!

Answer 2

Stage direction refers to an instruction that is written in the script of the play indicating the movement of the characters and stage actions. Also, it is also referred to as the stage director techniques.

Stage direction in a play gives the motivation regarding the actions of the characters.

Hence,  line in this excerpt from Act I, scene I, of Richard III which depicts stage direction is "(Enter CLARENCE, guarded, and BRAKENBURY)"

The stage direction of Clarence provides direction as to how Clarence entered guarded in the scene and gives the motivation regarding such action of Clarence.