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?