Vacuous celebrity advertising American island (6)
I believe the answer is:
cyprus
'island' is the definition.
(Cyprus is an island)
'vacuous celebrity advertising american' is the wordplay.
'vacuous' means to remove the middle letters.
'advertising' becomes 'PR' (public relations).
'american' becomes 'us' (abbreviation for United States).
'celebrity' with its middle taken out is 'cy'.
'cy'+'pr'+'us'='CYPRUS'
(Other definitions for cyprus that I've seen before include "Mediterranean country, capital Nicosia" , "Partitioned Med. island" , "Large East Mediterranean island" , "Aphrodite's island" , "Mediterranean island country" .)