Notice picked up in Hayling Island (4)
I believe the answer is:
sign
'notice' is the definition.
(I've seen this before)
'picked up in hayling island' is the wordplay.
'picked up' says the letters should be written backwards.
'in' indicates a hidden word.
'ngis' is hidden in the letters of 'hayling island'.
'ngis' reversed gives 'SIGN'.
(Other definitions for sign that I've seen before include "Leo, for instance" , "Traffic control - to write one's name" , "Public notice; Leo, say" , "Omen or indication" , "Communicate silently" .)