Island discovered by Magellan (4)
I believe the answer is:
guam
'island discovered by magellan' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for guam that I've seen before include "Largest of the Mariana Islands" , "NW Pacific island with large US base" , "North Pacific island, base for the US navy and air force" , "Island in the West Pacific" , "US island east of the Philippines" .)