Advertise (4)
'advertise' is the definition.
(I know that plug is a more specific form of advertise)
This is the entire clue.
(Other definitions for plug that I've seen before include "Device put into socket" , "Piece of publicity" , "Piece of chewing tobacco" , "Piece of tobacco; block" , "Favourable mention" .)
'advertise' is the definition.
(I know that advertise can be written as publicise)
This is all the clue.