Left-winger picked up information on radio (3)
I believe the answer is:
red
'left-winger' is the definition.
(red can mean a leftwing person)
'picked up information on radio' is the wordplay.
'picked up information' becomes 'read' (eg read in a book).
'on radio' shows a homophone (sound like).
'read' sounds like 'RED'.
(Other definitions for red that I've seen before include "Blushing" , "lefty" , "14 -- breed of 4" , "Merchant flag" , "Colour of garnets" .)