Direst sort of pace (6)
I believe the answer is:
Here is my best explanation:
'pace' is the definition.
('stride' can be a synonym of 'pace')
'direst sort' is the subsidiary indication.
'sort' indicates an anagram.
'direst' with letters rearranged gives 'stride'.
'of' is the link.
(Other definitions for stride that I've seen before include "Move with long steps", "A lengthy step", "Long walking step", "Direst kind of long step", "Take long steps", "Step out energetically", "Take long paces", "Long step of direst kind", "Pace" and "A long step".)