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 "jazz piano-playing", "Direst kind of long step", "Long pace", "A long step", "Walk along in direst way", "Pace", "style of jazz piano", "Take long steps", "A lengthy step" and "A big step forward".)