Plug — promote (4)
I believe the answer is:
tout
This clue is a double definition.
'plug' is the first definition.
(I've seen this in another clue)
'promote' is the second definition.
(I've seen this in another clue)
(Other definitions for tout that I've seen before include "Solicit (business) brazenly" , "Solicit custom brazenly" , "Profiteering ticket seller" , "Seller of racing tips etc" , "Attempt to sell, perhaps by pestering" .)