Notice pal sent message (7)
I believe the answer is:
placard
'notice' is the definition.
(I know that notice can be written as placard)
'pal sent message' is the wordplay.
'sent' indicates anagramming the letters (send can mean to excite or stimulate).
'message' becomes 'card' (card is a kind of message).
'pal' with letters rearranged gives 'pla'.
'pla'+'card'='PLACARD'
(Other definitions for placard that I've seen before include "Slogan or message of protest on board" , "Sign posted in a public place as an advertisement" , "Notice carried for public display" , "Sign for public display" , "Large portable notice" .)