Progressive permission to proceed (2-5)
I believe the answer is:
go-ahead
I believe this clue is a double definition.
'progressive' is the first definition.
(I've seen this before)
'permission to proceed' is the second definition.
(I've seen this before)
(Other definitions for go-ahead that I've seen before include "Enterprisingly progressive" , "Pioneering (green light?)" , "Up-and-coming - authorisation" , "Enterprising" , "Permission to proceed" .)