weened > supposed
2 And hoped to reap the crop of all my care, 3 Into new woes unweeting I was cast
unweeting > ignorant, unwitting
4 By this false faitour, who unworthy wears
faitour > impostor, cheat wears > bears, carries
5 His worthy shield, whom he, with guileful snare,
His > [Sansfoy's] he > [the Redcross Knight]
6 Entrapped slew, and brought to shameful grave.
Entrapped slew > [Killed while trapped]
7 Me, silly maid, away with him he bore,