disdain > indignation, anger [… at]
3 Of his hard hap, did vex his noble breast,
hap > fortune, lot
4 And thousand fancies beat his idle brain
idle > inactive; empty
5 With their light wings, the sights of semblants vain:
sights > appearances, visions semblants > images vain > weak, foolish; unavailing
6 Oft did he wish that lady fair might be
that > [that that]
7 His Faery Queen, for whom he did complain: