Mull, eg (4)
I believe the answer is:
isle
'mull eg' is the definition.
(I know that Isle of Mull is a isle)
This is all the clue.
(Other definitions for isle that I've seen before include "This could be key" , "Detached territory" , "Insular place" , "Anglesey, say" , "Rum, for example" .)