3 His beast he felly pricked on either side,
felly > fiercely, hotly pricked > spurred
4 And his mischievous bow full ready bent,
mischievous > {Producing or intending harm} full > very, quite
5 With which at him a cruel shaft he sent:
shaft > arrow
6 But he was wary, and it warded well
he > [Arthur]
7 Upon his shield, that it no further went,
that > [so that]