3 With their rude hands and grisly grapplement,

rude > rough, clumsy; violent grisly > horrible, fearsome grapplement > grappling; clutch, grasp (WU)

4 Till the villein, coming to their aid,

villein > villain, serf

5 Upon him fell, and load upon him laid; 6 Full little wanted, but he had him slain,

Full little wanted, but he had him slain > [Maleger very nearly killed him; "full" = "very", "wanted" = "lacked">[

7 And of the battle baleful end had made,

baleful > deadly, unhappy

8 Had not his gentle squire beheld his pain,

his > [Arthur's] gentle > noble