Notice head of pin left by a joker (7)
I believe the answer is:
placard
'notice' is the definition.
(I know that notice can be written as placard)
'head of pin left by a joker' is the wordplay.
'head of' indicates taking the first letters.
'left by' becomes 'l' (I've seen this in other clues).
'joker' becomes 'card' (joker is a type of playing card).
The initial letter of 'pin' is 'p'.
'p'+'l'+'a'+'card'='PLACARD'
(Other definitions for placard that I've seen before include "Sign for public display" , "Slogan or message of protest on board" , "One taken on march" , "what may be carried in a demo" , "Poster" .)