Ad writer's award (4)
I believe the answer is:
clio
'ad writer's award' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for clio that I've seen before include "Muse of history (from Renault?)" , "Muse of history - car" , "One of the Muses" , "inspiration for historians" , "In Greek and Roman myth, the Muse of history" .)