Sound of hooter across island (5)
I believe the answer is:
noise
'sound' is the definition.
(noise is a kind of sound)
'hooter across island' is the wordplay.
'hooter' becomes 'nose' (I've seen this before).
'across' means one lot of letters goes inside another.
'island' becomes 'i'.
'nose' enclosing 'i' is 'NOISE'.
'of' acts as a link.
(Other definitions for noise that I've seen before include "Virgil's birthplace" , "Unstructured sound" , "Uproar" , "Hubbub" , "Public talk" .)