Italian physicist taking brandy on island (7)
I believe the answer is:
marconi
'italian physicist' is the definition.
(Guglielmo Marconi)
'taking brandy on island' is the wordplay.
'taking' becomes 'on' (eg one taking drugs is 'on' drugs).
'brandy' becomes 'marc' (marc is a kind of brandy).
'on' is a charade indicator (letters next to each other).
'island' becomes 'i'.
'on' after 'marc' is 'marcon'.
'marcon'+'i'='MARCONI'
(Other definitions for marconi that I've seen before include "Italian scientist" , "Developer of radio telegraphy" , "Communications pioneer" , "Italian inventor of radio" , "Wireless inventor from Minorca" .)