4 The smouldering dust did round about him smoke,

smouldering > smothering, choking

5 Both horse and man nigh able to choke;

able > liable

6 And fairly couching his steel-headed spear,

fairly > expertly couching > {Lowering and placing in its rest}

7 Him first saluted with a sturdy stroke;

sturdy > recklessly violent

8 It booted naught, Sir Guyon coming near,

booted > availed