Chief road to progress? (7)
I believe the answer is:
headway
'progress?' is the definition.
(I know that headway is a type of advance)
'chief road' is the wordplay.
'chief' becomes 'head' (synonyms).
'road' becomes 'way' (I've seen this in other clues).
'head'+'way'='HEADWAY'
'to' is the link.
(Other definitions for headway that I've seen before include "make progress" , "Advance" , "Ground" , "Progress, forward movement" , "Progress or forward motion" .)