Showing initiative to embark on parking revolution (12)
I believe the answer is:
enterprising
'showing initiative' is the definition.
(I've seen this before)
'embark on parking revolution' is the wordplay.
'embark on' becomes 'enter' (I've seen this in another clue).
'parking' becomes 'p' (abbreviation on road signs).
'revolution' becomes 'rising'.
'enter'+'p'+'rising'='ENTERPRISING'
'to' is the link.
(Other definitions for enterprising that I've seen before include "Showing initiative" , "Adventurous, resourceful" , "Go ahead" , "Go-getting" , "Adventurous and imaginative" .)