Stride being broken is most ironic (6)
I believe the answer is:
driest
'most ironic' is the definition.
('dry' can be a synonym of 'ironic')
'stride being broken' is the wordplay.
'being broken' indicates anagramming the letters.
'stride' anagrammed gives 'DRIEST'.
'is' is the link.
(Other definitions for driest that I've seen before include "with least rainfall" , "Most arid - take it in stride" , "Least moist" .)