Wireless pioneer (7)
I believe the answer is:
'wireless pioneer' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for marconi that I've seen before include "Pioneer of radio communication from Minorca" , "Guglielmo --, inventor" , "Developer of radio telegraphy" , "Wireless inventor from Minorca" , "Italian electrical engineer, d. 1937" .)