Spoke about Darius (6)
I believe the answer is:
radius
'spoke' is the definition.
('radius' can be a synonym of 'spoke')
'about darius' is the wordplay.
'about' is an anagram indicator.
'darius' anagrammed gives 'RADIUS'.
(Other definitions for radius that I've seen before include "Centre-circumference length" , "It runs from the centre to the circumference" , "Part of build-up of arms" , "Distance from centre to circumference of circle" , "Straight line from circle's centre to circumference" .)