Impel a man possessed, okay (2-5)
I believe the answer is:
go-ahead
'okay' is the definition.
(I've seen this in another clue)
'impel a man possessed' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'man' could be 'ad' and 'ad' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for go-ahead that I've seen before include "Enterprising" , "Permission to proceed" , "Enterprisingly progressive" , "Pioneering (green light?)" , "Up-and-coming - authorisation" .)