Notice car lad covers after parking (7)
I believe the answer is:
placard
'notice' is the definition.
(synonyms)
'car lad covers after parking' is the wordplay.
'covers' means one lot of letters goes inside another.
'after' says to put letters next to each other.
'parking' becomes 'p' (abbreviation on road signs).
'car' placed inside 'lad' is 'lacard'.
'lacard' after 'p' is 'PLACARD'.
(Other definitions for placard that I've seen before include "Sign for public display" , "One taken on march" , "Large portable notice" , "Notice carried for public display" , "Bill" .)